Scandinavian Journal of Clinical & Laboratory Investigation, 2014; 74: 81–88
ORIGINAL ARTICLE
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Neutrophil gelatinase-associated lipocalin (NGAL) for the early detection of contrast-induced nephropathy after percutaneous coronary intervention
CHRISTOPH LIEBETRAU1*, LUISE GAEDE1*, OLIVER DOERR2, JOHANNES BLUMENSTEIN1, JOHANNES RIXE2, OLAF TEICHERT1, MATTHIAS WILLMER1, MICHAEL WEBER1, ANDREAS ROLF1,2, HELGE MÖLLMANN1,2, CHRISTIAN HAMM1,2 & HOLGER NEF1,2 1Kerckhoff
Heart and Thorax Center, Department of Cardiology, Bad Nauheim, and 2Justus-Liebig University of Giessen, Faculty of Medicine, Department of Cardiology and Angiology, Giessen, Germany
Abstract Background. Contrast-induced acute kidney injury (CI-AKI) occurs in up to 13% of patients undergoing percutaneous coronary intervention (PCI). Neutrophil gelatinase-associated lipocalin (NGAL) is an early biomarker for renal impairment. We investigated whether increased urinary NGAL concentrations were predictive of CI-AKI within 2 days after PCI or of a higher re-hospitalization rate within 9 months. Methods. Consecutive patients (n ⫽ 128), with stable coronary heart disease and eGFR ⱖ 30 mL/min/1.73 m2, undergoing PCI were included. Venous serum samples for measurement of creatinine, blood urea nitrogen, and cystatin C and urine samples for NGAL measurement were collected 4 hours and 1 and 2 days after contrast medium application. Patients were followed over 9 months to determine clinical endpoints. Results. CI-AKI was observed in 14 patients (10.9%) after PCI. NGAL concentrations before PCI were significantly higher in patients with subsequent CI-AKI (19.8 ng/mL [14.4–35.8] vs. 11.6 ng/mL [5.6–28.2]; p ⫽ 0.04). There was no significant difference in NGAL concentrations 4 h after PCI between patients with and without CI-AKI. One day after PCI, NGAL concentrations were significant higher in patients developing CI-AKI (100.1 ng/mL [41.5–129.2] vs. 16.6 ng/mL [9.1–28.1]; p ⬍ 0.001). Compared to common biomarkers, NGAL best predicted CI-AKI (AUC 0.939 [95% CI 0.89–0.99; p ⬍ 0.001]). The re-hospitalization rate due to progressive renal insufficiency within 9 months was higher in the group with CI-AKI than the group without (4 [28.6%] vs. 4 [3.5%], p ⬍ 0.01). Conclusion. Urinary NGAL is a biomarker for predicting CI-AKI when measured 1 day after PCI. Key Words: Contrast-induced acute kidney injury, contrast-induced nephropathy, percutaneous coronary intervention, neutrophil gelatinase-associated lipocalin, LCN2
Introduction The annual numbers of coronary angiographies and percutaneous coronary interventions (PCI) are steadily increasing [1,2]. The overall incidence of contrast-induced acute kidney injury (CI-AKI) after PCI ranges widely (3.3–13.0%) [3–7]. Especially at risk for CIAKI are patients with comorbidities, such as diabetes, anemia, congestive heart failure, chronic kidney disease (CKD), or hypertension [3,4,6,7]. These comorbidities appear more frequently with age, especially in elderly women [6]. Consequently, as life expectancies
increase, so will the number of the patients at risk for CI-AKI. Thus, CI-AKI is expected to occur more frequently in the future [5,6,12,13,24,25]. CI-AKI is known to have an adverse prognostic impact on patients after PCI [8]. Even transient renal dysfunction after PCI results in higher short and long-term mortality [9]. In contrast with other serious conditions like acute myocardial infarction, the onset of renal impairment is generally asymptomatic; therefore, the primary diagnosis is based on biomarkers. However, routine clinical diagnosis of acute kidney
*These authors contributed equally to this paper. Correspondence: Christoph Liebetrau, MD, Kerckhoff Heart and Thorax Center, Department of Cardiology, Benekestr. 2-8, 61231 Bad Nauheim, Germany. Tel: ⫹ 49 6032 9960. Fax: ⫹ 49 6032 996 2313. E-mail: [email protected] (Received 22 May 2013 ; accepted 12 September 2013) ISSN 0036-5513 print/ISSN 1502-7686 online © 2014 Informa Healthcare DOI: 10.3109/00365513.2013.860615
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injury (AKI) with common biomarkers such as serum creatinine (sCr) or blood urea nitrogen (BUN) is complicated by a diagnostic gap in the first hours after kidney injury. Animal studies have shown that AKI can be prevented if diagnosed early in the course of disease within the first hours after renal injury, before sCr rises [10,11]. NGAL (neutrophil gelatinase-associated lipocalin) is an early, possibly even real-time marker for a structural renal injury [20,21]. NGAL is highly sensitive; thus, it can be used to detect even minor kidney injuries [15,16,21,32]. As a result, it could be a future prognostic factor for renal function, outperforming sCr as well as cystatin C [21,31]. However, there are limited data on NGAL measurements after PCI, with varying results for the prediction of CI-AKI [26]. Therefore, the primary aim of the present study was to examine whether a difference in baseline or a rise in urinary NGAL concentration 4 h and 1 day after PCI predict subsequent CI-AKI (defined below) and have predictive value regarding morbidity, when defined as rehospitalization due to progressive renal insufficiency within 9 months of follow-up.
Materials and methods From October 2010 until August 2011, 128 consecutive patients undergoing elective PCI were included. Patients with an estimated glomerular filtration rate (eGFR) ⬍ 30 mL/min/1.73 m2 body surface were excluded. We assessed the clinical history, physical examination results, laboratory tests, and echocardiography for all patients. Patients received 500 mL NaCl 0.9% intravenously before and after PCI. PCI was performed in accordance with standard clinical practice. Patients were followed for 9 months after PCI. The primary endpoint was CI-AKI 2 days after PCI; while, the secondary endpoint was re-hospitalization due to progressive renal failure after 9 months. Follow-up data were collected during an in-person interview at the clinic for 94% of patients. Information about the remaining 6% of patients was collected by telephone conversations with the patients, their relatives, or their general physicians. All patients enrolled in the study signed informed consent, which included consent for biomarker analyses. The ethical board of the state of Hessen, Germany, approved the study (FF 57/2010).
biomarker mentioned above. The analyses were performed in one batch. The eGFR calculation was based on a simplified MDRD formula used in our hospital based on sCr concentration (eGFR (mL/min/L,73m 2 ) ⫽ 186 ⫻ S-Cr ⫺1,154 ⫻ age ⫺0,203 [⫻ 0.742 if female] [⫻ 1.21 if black]). Cystatin C was measured by a particle-enhanced turbidimetric immunoassay (PETIA) using ARCHITECT cystatin C latex enhanced reagents on the ARCHITECT c8000 (Abbott Laboratories, Abbott Park, IL, USA). The limit of detection for this assay is 0.05 mg/L. The precision is ⬍ 5.0% total coefficient of variation (CV) for concentrations ⱕ 1.0 mg/L and ⬍ 4.0% total CV for concentrations ⬎ 1.0 mg/L. As described in the package insert, the reference range for patients ⱖ 50 years of age is 0.40–0.99 mg/L. Urinary NGAL was assayed with a chemiluminescent microparticle immunoassay on the ARCHITECT i2000SR analyzer, which detects NGAL up to 1500 ng/mL (Abbott, Laboratories, Abbott Park, IL, USA). According to the package insert, the limit of detection for this assay ranges from 0.7–1.0 ng/mL. The reference range for patients 50 years and older is 4.0–99.0 ng/mL. Urinary NGAL concentrations ⬎ 99.0 ng/mL were considered as elevated. Grenier et al. could show a coefficient of variation (CV) for low concentration samples (mean 19.7 ng/ mL) ranging from 3.4–5.3%, for the medium concentration samples (mean 385.0 ng/mL) from 2.1–3.7% and for the high concentration samples (mean 1170– 1215 ng/mL) from 2.2–3.0%. The sensitivity, defined as the NGAL concentration corresponding to a 20% total CV, was ⬍ 2.0 ng/mL [32]. Definition of AKI The diagnosis of post-interventional CI-AKI was made in accordance with the international Kidney Disease: Improving Global Outcomes (KDIGO) definition of AKI [25]. AKI Stage 1 is defined as when sCr rises by ⱖ 26.0 μmol/L within 48 h, when sCR rises ⱖ 1.5-fold from the reference value, or urine output is ⬍ 0.5 mL/kg/h for ⬎ 6 consecutive hours. AKI Stage 2 is defined as a 2.0 -to 2.9-fold increase of sCr or urine output ⬍ 0.5 mL/kg/h for ⬎ 12 consecutive hours. AKI Stage 3 is defined when sCr rises is above 354.0 μmol/L or sCr increases ⱖ 3.0-fold, renal replacement therapy commences irrespective of stage, urine output ⬍ 0.3 mL/kg/h for ⬎ 24 h, or anuria is present for at least 12 h.
Laboratory assessment Venous blood samples for the determination of sCr, cystatin C, and BUN, and urine samples for measuring NGAL were collected prior to, 4 h after, as well as on the morning of the 1st and 2nd day after PCI. Samples were processed immediately and frozen at ⫺ 80°C until assayed. The specimens were thawed for the first time for the determination of the
Statistical analysis All data for continuous variables are expressed as mean ⫾ SD or as median and interquartile range as appropriate. Categorical variables are reported as number and percentage. After testing for normal distribution, values were compared by unpaired
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NGAL for CI-AKI after PCI Student’s t-tests or by Mann-Whitney-test. Fisher’s exact test or Chi-square test was used for categorical variables with nominal scales. To evaluate the performance of NGAL as a predictor of the diagnosis of CI-AKI, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve was plotted. Multivariate Cox regression analysis was used to calculate Hazard ratios. Univariate Cox regression analyses were performed with CI-AKI as the outcome variable. The following univariate predictors were tested: Age, gender, hypertension, hyperlipoproteinemia, diabetes mellitus, current smoker, family history of coronary artery disease, left ventricular ejection fraction, contrast medium amount, sCr, BUN, eGFR, cystatin C, and NGAL on admission, directly after, and one day after PCI. Univariate predictors with p-values ⱕ 0.10 were entered into multivariate Cox regression analysis. For the clinical endpoint analyses, the Kaplan-Meier method and log-rank test were applied. All statistical tests were performed two-tailed, and a p-value ⬍ 0.05 was considered statistically significance. For all statistical analyses, SPSS 19.0 (Statistical Package for the Social Sciences, Chicago, IL, USA) for Windows was used. Results A total of 128 consecutive patients were included. Table I shows the clinical characteristics of all patients enrolled in the study. Patients who developed CIAKI according to the KDIGO criteria within 2 days after PCI were assigned to the CI-AKI group (n ⫽ 14) and those who did not were assigned to the non-CIAKI group (n ⫽ 114). Patients developing CI-AKI were older and more patients showed an impaired renal function (CKD stage 3). No other significant differences were observed between the two groups for the other baseline characteristics shown in Table I. In addition, the concentrations of eGFR, sCr, and BUN before PCI did not differ between groups. In contrast, baseline urinary NGAL (uNGAL) already showed significantly higher concentrations in patients developing CI-AKI (19.8 ng/mL [IQR 14.5–35.8] vs. 11.6 ng/mL [IQR 5.6–28.2]; p ⫽ 0.04) (Table II). Four hours after PCI, uNGAL concentrations decreased compared to baseline in the both the CIAKI and non-CI-AKI groups (Table II, Figure 1). On the 1st day after PCI, uNGAL concentrations were significantly increased in the CI-AKI group (100.1 ng/ mL [IQR 41.5–129.2] vs. 16.6 ng/mL [IQR 9.1–28.1]; p ⬍ 0.001). In the non CI-AKI group the uNGAL concentrations 1 day after PCI did not differ significantly. There were 6 (0.5%) patients without CI-AKI and uNGAL concentrations above 99 ng/mL on the 1st day after PCI. Whereas 8 (57.1%) patients with uNGAL concentrations above 99 ng/mL could be observed in the CI-AKI group. On the 2nd day after PCI, uNGAL concentrations were still significantly elevated but already decreasing in the CI-AKI group
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Table I. Baseline characteristics. non-CI-AKI n ⫽ 114
CI-AKI n ⫽ 14
p value
Age (years), mean 68.7 ⫾ 10.5 (SD) Male sex, n (%) 87 (76.3) Cardiovascular risk factors, n (%) Hypertension 98 (86.0) Hypercholesterolemia 73 (64.0) Diabetes mellitus 45 (39.5) Current smoking 24 (21.1) Obesity 56 (49.1) Family disposition 25 (21.9) CKD, n (%) Stage 1 49 (43.0) Stage 2 40 (35.1) Stage 3 25 (21.9) LVEF (%), 49.4 ⫾ 9.7 mean (SD) Contrast fluid (mL), 147.9 ⫾ 74.5 mean (SD)
77.6 ⫾ 8.8
0.03
Variable
8 (57.1)
14 11 6 1 6 4
0.11
(100) (78.6) (42.9) (7.1) (42.9) (28.6)
0.23 0.55 0.55 0.06 0.78 0.49
4 (28.6) 3 (21.4) 7 (50.0) 53.9 ⫾ 8.4
0.07 0.43 ⬍ 0.01 0.14
155.4 ⫾ 73.2
0.73
CI-AKI, contrast-induced acute kidney injury; CKD, chronic kidney disease; LVEF, left ventricular ejection fraction.
(31.4 ng/mL [21.8–57.6] vs. 14.9 ng/mL [5.9–26.9]; p ⬍ 0.01); whereas, no difference could be observed in the non-CI-AKI group compared to baseline concentrations. The amount of contrast medium applied showed no correlation with the increase in uNGAL concentrations. Measurement of sCr (71.6 μmol/L IQR [60.1–127.3] vs. 76.0 μmol/L IQR [58.3–124.6]; p ⫽ 0.13), BUN (6.9 mmol/L IQR [5.5–12.4] vs. 6.7 mmol/L IQR [5.9–12.8]; p ⫽ 0.29) and cystatin C plasma concentrations (83.1 nmol/L IQR [64.4– 125.1] vs. 85.4 nmol/L IQR [65.2–119.1]; p ⫽ 0.09) revealed no significant increase 4 h after PCI in patients with CIN (Table II). The 1st day after PCI, cystatin C also showed a significant increase in patients with CI-AKI (74.2 nmol/L IQR [65.9–118.3] vs. 70.4 nmol/L IQR [63.7–87.6]; p ⫽ 0.001). SCR and BUN plasma concentrations showed no significant differences between the two groups at this timepoint (Figures 2 and 3). The 2nd day after PCI eGFR, cystatin C, BUN as well as sCr concentrations showed significant differences between the two groups. The ROC curves of the various biomarkers 1 day after PCI for the prediction of CI-AKI within 2 days after PCI are represented in Figure 4. Urinary NGAL provided the best result with an area under the receiver-operating characteristic curve (AUC) of 0.939 (95% CI 0.89–0.99; p ⬍ 0.001). In contrast, cystatin C showed an AUC of 0.681 (95% CI 0.49–0.88; p ⫽ 0.11), sCr an AUC ⫽ 0.701 (95% CI 0.58–0.91; p ⬍ 0.01) and BUN an AUC ⫽ 0.622 (95% CI 0.38–0.86; p ⫽ 0.28). The ROC curves of uNGAL before PCI and 4 h, 1 day and 2 days after PCI for the prediction of CI-AKI within 2 days after PCI are presented in Figure 5. Urinary NGAL 1 day after PCI provided the
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C. Liebetrau et al. Table II. Laboratory measurements.
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Variable Baseline, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L) 4 hours after PCI, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L) First day after PCI, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L) Second day after PCI, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L)
non-CI-AKI n ⫽ 114
CI-AKI n ⫽ 14
p value
11.6 68.9 87.5 77.8 6.5
(5.6–28.2) (62.2–86.9) (66.6–102.8) (68.1–91.9) (5.3–8.2)
19.8 85.4 84.4 76.0 6.7
(14.5–35.8) (65.2–119.1) (46.1–100.5) (58.3–124.6) (5.9–12.8)
0.04 0.09 0.39 0.96 0.30
7.7 68.2 91.2 72.5 6.4
(3.6–16.5) (61.4–85.4) (64.7–112.1) (64.5–88.4) (5.5–7.4)
11.0 83.1 88.3 71.6 6.9
(7.0–22.9) (64.4–125.1) (49.1–104.5) (60.1–127.3) (5.5–12.4)
0.08 0.09 0.10 0.13 0.29
16.6 70.4 86.2 80.4 6.2
(9.1–28.1) (63.7–87.6) (69.3–102.5) (68.1–90.2) (5.2–7.9)
100.1 74.2 71.4 89.3 6.6
(41.5–129.2) (65.9–118.3) (44.2–101.7) (71.6–133.5) (5.3–11.9)
⬍ 0.001 0.001 0.10 0.13 0.29
14.9 74.9 78.9 84.7 7.7
(5.9–26.9) (64.4–99.6) (58.8–97.9) (71.6–100.8) (5.3–9.0)
31.4 115.3 38.8 122.9 11.4
(21.8–57.6) (94.4–151.3) (26.9–76.1) (79.6–208.6) (8.7–15.0)
0.001 ⬍ 0.001 0.001 ⬍ 0.01 0.001
CI-AKI, contrast-induced acute kidney injury; eGFR, estimated glomerular filtration rate; NGAL, neutrophil gelatinase-associate lipocalin; PCI, percutaneous coronary intervention; BUN, blood urea nitrogen.
best result with an AUC of 0.939 (95% CI 0.89–0.99; p ⬍ 0.001). In contrast, uNGAL before PCI showed an AUC ⫽ 0.688 (95% CI 0.48–0.89; p ⫽ 0.08), and uNGAL 4 h after PCI an AUC of 0.565 (95% CI 0.37–0.77; p ⫽ 0.55), whereas uNGAL 2 days after PCI showed an AUC ⫽ 0.786 (95% CI 0.65–0.93; p ⫽ 0.008).
Cox regression analysis revealed that the risk of CI-AKI during 2 days after PCI was higher when patients were older (hazard ratio (HR) 1.12; p ⫽ 0.04) or uNGAL was increased the 1st day after PCI (HR 1.02; p ⬍ 0.001) (Table III). Surprisingly, patients with pre-existing CKD were not at higher risk for CI-AKI in our cohort.
Figure 1. Neutrophil gelatinase-associated lipocalin (NGAL) urine concentrations (median fold-change [IQR]) of all patients at baseline and throughout the study. Light-colored bars indicate patients with contrast-induced acute kidney injury (CI-AKI) and grey-colored bars indicate patients without CI-AKI.
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NGAL for CI-AKI after PCI
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Figure 2. Serum creatinine (sCR) concentrations (median fold-change [IQR]) of all patients at baseline and throughout the study. Lightcolored bars indicate patients with contrast-induced acute kidney injury (CI-AKI) and grey-colored bars indicate patients without CI-AKI.
Follow-up During the 9-months of follow-up, the re-hospitalization rate due to progressive renal insufficiency among the patients in the CI-AKI group was significantly higher (4 [28.6%] vs. 4 [3.5%], p ⬍ 0.01) than the non-CI-AKI group. NGAL concentrations the 1st day after PCI had no predictive value on re-hospitalization within 9 months.
Discussion The majority of coronary angiographies and PCI are performed as outpatient services today. Due to
the diagnostic gap of commonly used biomarkers, patients developing CI-AKI might be missed because of discharge on the day of the intervention. Therefore, the aim of the present study was to analyze whether measurement of uNGAL in the first hours after PCI predicts CI-AKI after PCI earlier and more sensitively than common biomarkers. Our study showed that uNGAL is a biomarker for the early risk stratification of CI-AKI after PCI and is superior to sCr for the early detection of CIAKI. An interesting point of our study is, that the median uNGAL concentration at baseline was significantly higher in patients developing subsequent CI-AKI, but with a large overlap between the groups
Figure 3. Blood urea nitrogen (BUN) serum concentrations (median fold-change [IQR]) of all patients at baseline and throughout the study. Light-colored bars indicate patients with contrast-induced acute kidney injury (CI-AKI) and grey-colored bars indicate patients without CI-AKI.
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C. Liebetrau et al. Table III. Hazard ratios and 95% CIs on logarithmic scale for prediction of contrast-induced acute kidney injury (CI-AKI). Variable
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age CKD Cystatin C 4 hours NGAL 4 hours eGFR first day Creatinine first day BUN first day Cystatin C first day NGAL first day
HR
CI lower
95% upper
p value
1.12 0.34 0.47 0.96 0.98 2.14 1.00 2.04 1.02
1.00 0.06 0.01 0.93 0.92 0.05 0.95 0.13 1.01
1.24 2.03 31.50 0.99 1.05 86.34 1.06 31.69 1.03
0.04 0.24 0.73 0.03 0.58 0.69 0.88 0.61 0.001
95% CI, 95% confidence interval; BUN, blood urea nitrogen; CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; HR, hazard ratio; NGAL, neutrophil gelatinaseassociated lipocalin.
Figure 4. Receiver operating characteristic (ROC) curves of the various biomarkers 1 day after PCI for the prediction of contrastinduced acute kidney injury (CI-AKI) within 2 days after PCI.
making it difficult to truly discriminate patients being at risk for CI-AKI. Nevertheless sCr, which is used in daily clinical practice, and cystatin C showed no differences between the groups at baseline. Prior studies have shown that uNGAL is a marker for minor renal injuries [15,16,21]. Patients with impaired renal function are known to be at higher risk for CI-AKI [3,6]; thus, uNGAL determination prior to PCI could indicate patients with normal sCr concentrations being at risk for CI-AKI. This is even
Figure 5. Receiver operating characteristic (ROC) curves of urinary neutrophil gelatinase-associated lipocalin (uNGAL) before percutaneous coronary intervention (PCI) and 4 h, 1 day and 2 days after PCI for the prediction of contrast-induced acute kidney injury (CI-AKI) within 2 days after PCI.
more important when patients are treated in outpatient care and worse outcomes due to missed CI-AKI might be avoided. However, this needs to be validated in a large-scale real-world scenario. Despite published data demonstrating uNGAL is a real-time marker [15,20], our data clearly demonstrate that uNGAL concentrations 4 h after elective PCI showed neither a significant difference nor increase in the CI-AKI group compared with the nonCI-AKI group. This is inconsistent with prior results, which showed uNGAL concentrations increase within 4 h after PCI [19,22,26]. The decrease of uNGAL concentrations was present in both groups and might be explainable by the hydration prior to and after PCI. Hydration status is a key factor in kidney function, urinary output, and damage, and in the development of CI-AKI. Urinary NGAL as a marker of tubular damage depends on these parameters as well. Furthermore, because of the dilution effect by hydration and/or by the contrast medium itself we could not observe any reduction of the kidney function by measuring sCR, BUN, cystatin C as well as by estimated GFR during the very early period after PCI. Because of the inaccurate definition of the exact time point of the beginning of kidney injury, the early release kinetics of uNGAL is entirely unknown. Therefore, repetitive measurements of uNGAL are required to definitely rule-out and rule-in CI-AKI. Nevertheless in patients with adequate hydration during PCI the very early measurement of uNGAL 4 h after PCI does not seem to be of value for predicting CI-AKI. The 1st day after PCI, uNGAL and cystatin C concentrations rose significantly in the CI-AKI group. In comparison to the uNGAL baseline values, the median uNGAL concentrations the 1st day after PCI were highly significant different with only few overlap between patients with and without CI-AKI allowing an adequate discrimination. Based on the AUCs of the various biomarkers, uNGAL was the strongest independent predictor of subsequent CIAKI 1 day after PCI, outperforming cystatin C and sCr. The overall increase and the total uNGAL con-
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NGAL for CI-AKI after PCI centrations were lower than expected [19,22], but still comparable to those seen in previous studies [18,26,38,31]. The higher uNGAL concentrations in other studies might be explained by comorbidities, higher amounts of contrast medium, and worse hydration statuses causing more kidney injuries and a higher overall incidence of CI-AKI. However, even with the lower increase, urinary NGAL was the most powerful predictor of CI-AKI in our study. However, regarding the hydration treatment to avoid CI-AKI further investigations are needed to determine the best time for measuring uNGAL after PCI. Clinical outcome in terms of re-hospitalization due to progressive renal insufficiency was better in patients without CI-AKI, which is consistent with the results of previous studies [5,6,9]. Contrary to other studies, uNGAL concentrations could not predict re-hospitalization in our cohort. Previously, concentrations at 6 h after contrast medium application were associated with a longer hospital stay, longer ICU stay, and higher risk for dialysis and death [28,29]. These results again confirm that uNGAL determination 4 h after PCI is not a useful time point for collecting samples. Nevertheless, regarding the follow-up data, our findings highlight the urgent necessity to treat patients at risk for CI-AKI to avoid adverse outcomes. With the higher diagnostic sensitivity of uNGAL, earlier diagnosis or maybe even prediction of CI-AKI with individual risk stratification and individualized therapy seems possible. Despite these promising results one must also remind that uNGAL is known to be elevated due to different circumstances. NGAL mRNA is normally expressed in a variety of adult human tissues, including bone marrow, uterus, prostate, salivary gland, stomach, colon, trachea, lung, liver and kidney [33]. In this context it is also known to be elevated in a number of human cancers, where it often represents a predictor of poor prognosis [34]. In addition, uNGAL is a part of the innate immune response due to bacterial infection and it acts also as a growth factor. Therefore of the increase of NGAL concentrations might not always be due to renal impairment. Decavale et al. could show this uNGAL increase in case of leucocyturia [35]. CI-AKI might therefore be more difficult to detect in case of systemic inflammation. This might especially be of interest in patients presenting with acute coronary syndrome. Urinary NGAL concentrations might be false positive in those patients due to the inflammatory response in case of acute myocardial infarction. To exclude false positive results for example leucocytes in urine and blood should be determined in addition to uNGAL. The results of our study should be interpreted in the context of several limitations. The laboratory results of conventional biomarkers like sCR and/or BUN in previous studies as well as in our study show a very low diagnostic sensitivity in terms of CI-AKI detection, but provide insight in daily clinical practice.
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The small number of enrolled consecutive patients from a single center is a major limitation of our study that must be considered. Due to the study size the number of events could be too low to draw definitive conclusions. Nevertheless the data are sufficient to demonstrate a significant increase in uNGAL concentrations with superiority to the conventional biomarkers the 1st day after PCI. Therefore further clinical investigations are necessary to determine firstly the best time point for uNGAL measurement after PCI if patients are hydrated sufficiently and secondly how CI-AKI might be avoided by preventive treatment. Conclusion Urinary NGAL is a biomarker for early risk stratification of CI-AKI after PCI. It may be able to predict CI-AKI prior to contrast medium application. However, it is not a real-time marker for CI-AKI after PCI. Prospective studies are needed to investigate whether uNGAL concentrations could be used as the basis for prophylactic or early interventional strategies to prevent CI-AKI after PCI. Acknowledgements Abbott Diagnostics donated urinary NGAL and cystatin C assays. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. The funding sources were not involved in the design of the trial, the gathering, analysis and interpretation of data, the writing of the manuscript or the decision to publish the paper.
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C. Liebetrau et al. Garrat KN, Holmes DR. Incidence and prognostic importance of acute renal failure after percutaneous coronary intervention. Circulation 2002;105:2259–64. Sidhu RB, Brown JR, Robb JF, Jayne JE, Friedman BJ, Hettleman BD, Kaplan AV, Niles NW, Thompson CA. Interaction of gender and age on post cardiac catheterization contrast-induced acute kidney injury. Am J Cardiol 2008; 102:1482–6. Morabito S, Pistolesi V, Benedetti G, Di Roma A, Colantonia R, Mancone M, Sardella G, Cibelli L, Ambrosino M, Polistena F, Pierucci A. Incidence of contrast-induced acute kidney injury associated with diagnostic or interventional coronary angiography. J Nephrol 2012;25:1098–107. Le Feuvre C, Dambrin G, Helft G, Tabet S, Beygui F, Legendre C, Péraldi MN, Vacheron A, Metzger JP. Comparison of clinical outcome following coronary stenting or balloon angioplasty in dialysis versus non-dialysis patients. Am J Cardiol 2000;85:1365–8. Wi J, Ko YG, Kim JS, Kim BK, Choi D, Ha JW, Hong MK, Jang Y. Impact of contrast-induced acute kidney injury with transient or persistent renal dysfunction on long-term outcomes of patients with acute myocardial infarction undergoing percutaneous coronary intervention. Heart 2011;97:1753–7. Devarajan P. Update on mechanisms of ischemic acute kidney injury. Comprehensive review of the pathophysiologic mechanisms that underlie AKI. J Am Soc Nephrol 2006;17:1503–20. Devarajan P. Emerging biomarkers of acute kidney injury. Contrib Nephrol 2007;156:203–12. Wasen E, Isoaho R, Mattila K, Vahlberg T, Kivela SL, Irjala K. Estimation of glomerular filtration rate in the elderly: a comparison of creatinine-based formulae with serum cystatin C. J Int Med 2004;256:70–8. Coll E, Botey A, Alvarez L, Poch E, Quintó L, Saurina A, Vera M, Piera C, Darnell A. Serum cystatin C as a new marker for noninvasive estimation of glomerular filtration rate and as a marker for early renal impairment. Am J Kidney Dis 2000;36:29–34. Fliser D, Ritz E. Serum cystatin C concentration as a marker of renal dysfunction in the elderly. Am J Kidney Dis 2001:37:79–83. Emberson JR, Haynes R, Dasgupta T, Mafham M, Landray MJ, Baigent C, Clarke R. Cystatin C and risk of vascular and nonvascular mortality: a prospective cohort study of older men. J Intern Med 2010;268:145–54. Kjeldsen L, Cowland JB, Borregaard N. Human neutrophil gelatinase-associated lipocalin and homologous proteins in rat and mouse. Biochim Biophys Acta 2000;18:272–83. Supavekin S, Zhang W, Kucherlapati R, Kaskel FJ, Moore LC, Devarajan P. Differential gene expression following early renal ischemia/reperfusion. Kidney Int 2003;63:1714–24. Lavery AP, Meinzen-Derr JK, Anderson E, Ma Q, Bennett MR, Devarajan P, Schibler KR. Urinary NGAL in premature infants. Pediatr Res 2008;64:423–8. Bachorzewska-Gajewska H, Poniatowski B, Dobrzycki S. NGAL (neutrophil gelatinase-associated lipocalin) and L-FABP after percutaneous coronary interventions due to unstable angina in patients with normal serum creatinine. Adv Med Sci 2009;54:221–4. Devarajan P. Review: neutrophil gelatinase-associated lipocalin: a troponin-like biomarker for human acute kidney injury. Nephrology 2010;15:419–28.
Notice of correction The online version of this article published ahead of print on 5 Dec 2013 contained an error on page 6. The same image was published twice in figures 4 and 5. The error has been corrected for this version.
[21] Bolignano D, Donato V, Coppolino G, Campo S, Buemi A, Lacquaniti A, Buemi M. Neutrophil gelatinase-associated lipocalin (NGAL) as a marker of kidney damage. Am J Kidney Dis 2008;52:595–605. [22] Shaker O, El-Shehaby A, El-Khatib M. Early diagnostic markers for contrast nephropathy in patients undergoing coronary angiography. Angiology 2010;61:731–6. [23] Singer E, Elger A, Elitox S, Kettritz R, Nickolas T, Barasch J, Luft F, Schmidt-Ott K. Urinary neutrophil gelatinase-associated lipocalin distinguishes pre-renal from intrensic renal failure and predicts outcome. Kidney Int 2011;80:405–14. [24] Fliser D, Ritz E. Serum cystatin C concentration as a marker of renal dysfunction in the elderly. Am J Kidney Dis 2001; 37:79–83. [25] Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int (Suppl.)2012; 2:1–138. [26] Bachorzewska-Gajewska H, Malyszko J, Sitniewska E, Malyszko JS, Poniatowski B, Pawlak I, Dobrzycki S. NGAL (neutrophil gelatinase-associated lipocalin) and cystatin C: are they good predictors of contrast nephropathy after percutaneous coronary interventions in patients with stable angina and normal serum creatinine)? Int J Cardiol 2008;127;290–1. [27] Hemdahl A-L, Gabrielsen A, Zhu C, Eriksson P, Hedin U, Kastrup J, Thorén P, Hansson GK. Expression of neutrophil gelatinase-associated lipocalin in atherosclerosis and myocardial infarction. Arterioscler Thromb Vasc Biol 2006;26:136–42. [28] Kümpers P, Hafer C, Lukasz A, Lichtinghagen R, Brand K, Fliser D, Faulhaber-Walter R, Kielstein JT. Serum neutrophil gelatinase-associated lipocalin at inception of renal replacement therapy predicts survival in critically ill patients with acute kidney injury. Critical Care 2010;141:9. [29] Dent CL, Ma Q, Dastrala S, Bennett M, Mitsnefes MM, Barasch J, Devarajan P. Plasma neutrophil gelastinaseassociated lipocalin predicts acute kidney injury, morbidity and mortality after pediatric cardiac surgery: a prospective uncontrolled cohort study. Crit Care 2007;11:127. [30] Vanmassenhove J, Vanholder R, Nagler E, Van Biesen W. Urinary and serum biomarkers for the diagnosis of acute kidney injury: an in depth review of literature. Nephrol Dial Transpl 2013;28:254–73. [31] Liebetrau C, Dörr O, Baumgarten H, Gaede L, Szardien S, Blumenstein J, Rolf A, Möllmann H, Hamm CW, Walther T, Nef H, Weber M. Neutrophil gelatinse-associated lipocalin (NGAL) for the early detection of cardiac surgery associated acute kidney injury. Scan J Clin Lab Med 2013;73:392–9. [32] Grenier FC, Ali S, Syed H, Workman R, Martens F, Liao M, Wang Y, Wong PY. Evaluation of the ARCHITECT urine NGAL assay: assay performance, specimen handling requirements and biological variability. Clin Biochem 2009;43:615–20. [33] Cowland JB, Borregaard N. Molecular characterization and pattern of tissue expression of the gene for neutrophil gelatinase-associated lipocalin from humans. Genomics 1997; 45:17–23. [34] Devarajan P. Neutrophil gelatinase-associated lipocalin: new paths for an old shuttle. Cancer Ther 2007;5(B):463–70. [35] Decavale AS, Dhondt L, De Buyzere ML, Delanghe JR. Increased urinary neutrophil gelatinase associated lipocalin in urinary tract infecions and leukocyturia. Clin Chem Lab Med 2011;49:999–1003.
ORIGINAL ARTICLE
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Neutrophil gelatinase-associated lipocalin (NGAL) for the early detection of contrast-induced nephropathy after percutaneous coronary intervention
CHRISTOPH LIEBETRAU1*, LUISE GAEDE1*, OLIVER DOERR2, JOHANNES BLUMENSTEIN1, JOHANNES RIXE2, OLAF TEICHERT1, MATTHIAS WILLMER1, MICHAEL WEBER1, ANDREAS ROLF1,2, HELGE MÖLLMANN1,2, CHRISTIAN HAMM1,2 & HOLGER NEF1,2 1Kerckhoff
Heart and Thorax Center, Department of Cardiology, Bad Nauheim, and 2Justus-Liebig University of Giessen, Faculty of Medicine, Department of Cardiology and Angiology, Giessen, Germany
Abstract Background. Contrast-induced acute kidney injury (CI-AKI) occurs in up to 13% of patients undergoing percutaneous coronary intervention (PCI). Neutrophil gelatinase-associated lipocalin (NGAL) is an early biomarker for renal impairment. We investigated whether increased urinary NGAL concentrations were predictive of CI-AKI within 2 days after PCI or of a higher re-hospitalization rate within 9 months. Methods. Consecutive patients (n ⫽ 128), with stable coronary heart disease and eGFR ⱖ 30 mL/min/1.73 m2, undergoing PCI were included. Venous serum samples for measurement of creatinine, blood urea nitrogen, and cystatin C and urine samples for NGAL measurement were collected 4 hours and 1 and 2 days after contrast medium application. Patients were followed over 9 months to determine clinical endpoints. Results. CI-AKI was observed in 14 patients (10.9%) after PCI. NGAL concentrations before PCI were significantly higher in patients with subsequent CI-AKI (19.8 ng/mL [14.4–35.8] vs. 11.6 ng/mL [5.6–28.2]; p ⫽ 0.04). There was no significant difference in NGAL concentrations 4 h after PCI between patients with and without CI-AKI. One day after PCI, NGAL concentrations were significant higher in patients developing CI-AKI (100.1 ng/mL [41.5–129.2] vs. 16.6 ng/mL [9.1–28.1]; p ⬍ 0.001). Compared to common biomarkers, NGAL best predicted CI-AKI (AUC 0.939 [95% CI 0.89–0.99; p ⬍ 0.001]). The re-hospitalization rate due to progressive renal insufficiency within 9 months was higher in the group with CI-AKI than the group without (4 [28.6%] vs. 4 [3.5%], p ⬍ 0.01). Conclusion. Urinary NGAL is a biomarker for predicting CI-AKI when measured 1 day after PCI. Key Words: Contrast-induced acute kidney injury, contrast-induced nephropathy, percutaneous coronary intervention, neutrophil gelatinase-associated lipocalin, LCN2
Introduction The annual numbers of coronary angiographies and percutaneous coronary interventions (PCI) are steadily increasing [1,2]. The overall incidence of contrast-induced acute kidney injury (CI-AKI) after PCI ranges widely (3.3–13.0%) [3–7]. Especially at risk for CIAKI are patients with comorbidities, such as diabetes, anemia, congestive heart failure, chronic kidney disease (CKD), or hypertension [3,4,6,7]. These comorbidities appear more frequently with age, especially in elderly women [6]. Consequently, as life expectancies
increase, so will the number of the patients at risk for CI-AKI. Thus, CI-AKI is expected to occur more frequently in the future [5,6,12,13,24,25]. CI-AKI is known to have an adverse prognostic impact on patients after PCI [8]. Even transient renal dysfunction after PCI results in higher short and long-term mortality [9]. In contrast with other serious conditions like acute myocardial infarction, the onset of renal impairment is generally asymptomatic; therefore, the primary diagnosis is based on biomarkers. However, routine clinical diagnosis of acute kidney
*These authors contributed equally to this paper. Correspondence: Christoph Liebetrau, MD, Kerckhoff Heart and Thorax Center, Department of Cardiology, Benekestr. 2-8, 61231 Bad Nauheim, Germany. Tel: ⫹ 49 6032 9960. Fax: ⫹ 49 6032 996 2313. E-mail: [email protected] (Received 22 May 2013 ; accepted 12 September 2013) ISSN 0036-5513 print/ISSN 1502-7686 online © 2014 Informa Healthcare DOI: 10.3109/00365513.2013.860615
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injury (AKI) with common biomarkers such as serum creatinine (sCr) or blood urea nitrogen (BUN) is complicated by a diagnostic gap in the first hours after kidney injury. Animal studies have shown that AKI can be prevented if diagnosed early in the course of disease within the first hours after renal injury, before sCr rises [10,11]. NGAL (neutrophil gelatinase-associated lipocalin) is an early, possibly even real-time marker for a structural renal injury [20,21]. NGAL is highly sensitive; thus, it can be used to detect even minor kidney injuries [15,16,21,32]. As a result, it could be a future prognostic factor for renal function, outperforming sCr as well as cystatin C [21,31]. However, there are limited data on NGAL measurements after PCI, with varying results for the prediction of CI-AKI [26]. Therefore, the primary aim of the present study was to examine whether a difference in baseline or a rise in urinary NGAL concentration 4 h and 1 day after PCI predict subsequent CI-AKI (defined below) and have predictive value regarding morbidity, when defined as rehospitalization due to progressive renal insufficiency within 9 months of follow-up.
Materials and methods From October 2010 until August 2011, 128 consecutive patients undergoing elective PCI were included. Patients with an estimated glomerular filtration rate (eGFR) ⬍ 30 mL/min/1.73 m2 body surface were excluded. We assessed the clinical history, physical examination results, laboratory tests, and echocardiography for all patients. Patients received 500 mL NaCl 0.9% intravenously before and after PCI. PCI was performed in accordance with standard clinical practice. Patients were followed for 9 months after PCI. The primary endpoint was CI-AKI 2 days after PCI; while, the secondary endpoint was re-hospitalization due to progressive renal failure after 9 months. Follow-up data were collected during an in-person interview at the clinic for 94% of patients. Information about the remaining 6% of patients was collected by telephone conversations with the patients, their relatives, or their general physicians. All patients enrolled in the study signed informed consent, which included consent for biomarker analyses. The ethical board of the state of Hessen, Germany, approved the study (FF 57/2010).
biomarker mentioned above. The analyses were performed in one batch. The eGFR calculation was based on a simplified MDRD formula used in our hospital based on sCr concentration (eGFR (mL/min/L,73m 2 ) ⫽ 186 ⫻ S-Cr ⫺1,154 ⫻ age ⫺0,203 [⫻ 0.742 if female] [⫻ 1.21 if black]). Cystatin C was measured by a particle-enhanced turbidimetric immunoassay (PETIA) using ARCHITECT cystatin C latex enhanced reagents on the ARCHITECT c8000 (Abbott Laboratories, Abbott Park, IL, USA). The limit of detection for this assay is 0.05 mg/L. The precision is ⬍ 5.0% total coefficient of variation (CV) for concentrations ⱕ 1.0 mg/L and ⬍ 4.0% total CV for concentrations ⬎ 1.0 mg/L. As described in the package insert, the reference range for patients ⱖ 50 years of age is 0.40–0.99 mg/L. Urinary NGAL was assayed with a chemiluminescent microparticle immunoassay on the ARCHITECT i2000SR analyzer, which detects NGAL up to 1500 ng/mL (Abbott, Laboratories, Abbott Park, IL, USA). According to the package insert, the limit of detection for this assay ranges from 0.7–1.0 ng/mL. The reference range for patients 50 years and older is 4.0–99.0 ng/mL. Urinary NGAL concentrations ⬎ 99.0 ng/mL were considered as elevated. Grenier et al. could show a coefficient of variation (CV) for low concentration samples (mean 19.7 ng/ mL) ranging from 3.4–5.3%, for the medium concentration samples (mean 385.0 ng/mL) from 2.1–3.7% and for the high concentration samples (mean 1170– 1215 ng/mL) from 2.2–3.0%. The sensitivity, defined as the NGAL concentration corresponding to a 20% total CV, was ⬍ 2.0 ng/mL [32]. Definition of AKI The diagnosis of post-interventional CI-AKI was made in accordance with the international Kidney Disease: Improving Global Outcomes (KDIGO) definition of AKI [25]. AKI Stage 1 is defined as when sCr rises by ⱖ 26.0 μmol/L within 48 h, when sCR rises ⱖ 1.5-fold from the reference value, or urine output is ⬍ 0.5 mL/kg/h for ⬎ 6 consecutive hours. AKI Stage 2 is defined as a 2.0 -to 2.9-fold increase of sCr or urine output ⬍ 0.5 mL/kg/h for ⬎ 12 consecutive hours. AKI Stage 3 is defined when sCr rises is above 354.0 μmol/L or sCr increases ⱖ 3.0-fold, renal replacement therapy commences irrespective of stage, urine output ⬍ 0.3 mL/kg/h for ⬎ 24 h, or anuria is present for at least 12 h.
Laboratory assessment Venous blood samples for the determination of sCr, cystatin C, and BUN, and urine samples for measuring NGAL were collected prior to, 4 h after, as well as on the morning of the 1st and 2nd day after PCI. Samples were processed immediately and frozen at ⫺ 80°C until assayed. The specimens were thawed for the first time for the determination of the
Statistical analysis All data for continuous variables are expressed as mean ⫾ SD or as median and interquartile range as appropriate. Categorical variables are reported as number and percentage. After testing for normal distribution, values were compared by unpaired
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NGAL for CI-AKI after PCI Student’s t-tests or by Mann-Whitney-test. Fisher’s exact test or Chi-square test was used for categorical variables with nominal scales. To evaluate the performance of NGAL as a predictor of the diagnosis of CI-AKI, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve was plotted. Multivariate Cox regression analysis was used to calculate Hazard ratios. Univariate Cox regression analyses were performed with CI-AKI as the outcome variable. The following univariate predictors were tested: Age, gender, hypertension, hyperlipoproteinemia, diabetes mellitus, current smoker, family history of coronary artery disease, left ventricular ejection fraction, contrast medium amount, sCr, BUN, eGFR, cystatin C, and NGAL on admission, directly after, and one day after PCI. Univariate predictors with p-values ⱕ 0.10 were entered into multivariate Cox regression analysis. For the clinical endpoint analyses, the Kaplan-Meier method and log-rank test were applied. All statistical tests were performed two-tailed, and a p-value ⬍ 0.05 was considered statistically significance. For all statistical analyses, SPSS 19.0 (Statistical Package for the Social Sciences, Chicago, IL, USA) for Windows was used. Results A total of 128 consecutive patients were included. Table I shows the clinical characteristics of all patients enrolled in the study. Patients who developed CIAKI according to the KDIGO criteria within 2 days after PCI were assigned to the CI-AKI group (n ⫽ 14) and those who did not were assigned to the non-CIAKI group (n ⫽ 114). Patients developing CI-AKI were older and more patients showed an impaired renal function (CKD stage 3). No other significant differences were observed between the two groups for the other baseline characteristics shown in Table I. In addition, the concentrations of eGFR, sCr, and BUN before PCI did not differ between groups. In contrast, baseline urinary NGAL (uNGAL) already showed significantly higher concentrations in patients developing CI-AKI (19.8 ng/mL [IQR 14.5–35.8] vs. 11.6 ng/mL [IQR 5.6–28.2]; p ⫽ 0.04) (Table II). Four hours after PCI, uNGAL concentrations decreased compared to baseline in the both the CIAKI and non-CI-AKI groups (Table II, Figure 1). On the 1st day after PCI, uNGAL concentrations were significantly increased in the CI-AKI group (100.1 ng/ mL [IQR 41.5–129.2] vs. 16.6 ng/mL [IQR 9.1–28.1]; p ⬍ 0.001). In the non CI-AKI group the uNGAL concentrations 1 day after PCI did not differ significantly. There were 6 (0.5%) patients without CI-AKI and uNGAL concentrations above 99 ng/mL on the 1st day after PCI. Whereas 8 (57.1%) patients with uNGAL concentrations above 99 ng/mL could be observed in the CI-AKI group. On the 2nd day after PCI, uNGAL concentrations were still significantly elevated but already decreasing in the CI-AKI group
83
Table I. Baseline characteristics. non-CI-AKI n ⫽ 114
CI-AKI n ⫽ 14
p value
Age (years), mean 68.7 ⫾ 10.5 (SD) Male sex, n (%) 87 (76.3) Cardiovascular risk factors, n (%) Hypertension 98 (86.0) Hypercholesterolemia 73 (64.0) Diabetes mellitus 45 (39.5) Current smoking 24 (21.1) Obesity 56 (49.1) Family disposition 25 (21.9) CKD, n (%) Stage 1 49 (43.0) Stage 2 40 (35.1) Stage 3 25 (21.9) LVEF (%), 49.4 ⫾ 9.7 mean (SD) Contrast fluid (mL), 147.9 ⫾ 74.5 mean (SD)
77.6 ⫾ 8.8
0.03
Variable
8 (57.1)
14 11 6 1 6 4
0.11
(100) (78.6) (42.9) (7.1) (42.9) (28.6)
0.23 0.55 0.55 0.06 0.78 0.49
4 (28.6) 3 (21.4) 7 (50.0) 53.9 ⫾ 8.4
0.07 0.43 ⬍ 0.01 0.14
155.4 ⫾ 73.2
0.73
CI-AKI, contrast-induced acute kidney injury; CKD, chronic kidney disease; LVEF, left ventricular ejection fraction.
(31.4 ng/mL [21.8–57.6] vs. 14.9 ng/mL [5.9–26.9]; p ⬍ 0.01); whereas, no difference could be observed in the non-CI-AKI group compared to baseline concentrations. The amount of contrast medium applied showed no correlation with the increase in uNGAL concentrations. Measurement of sCr (71.6 μmol/L IQR [60.1–127.3] vs. 76.0 μmol/L IQR [58.3–124.6]; p ⫽ 0.13), BUN (6.9 mmol/L IQR [5.5–12.4] vs. 6.7 mmol/L IQR [5.9–12.8]; p ⫽ 0.29) and cystatin C plasma concentrations (83.1 nmol/L IQR [64.4– 125.1] vs. 85.4 nmol/L IQR [65.2–119.1]; p ⫽ 0.09) revealed no significant increase 4 h after PCI in patients with CIN (Table II). The 1st day after PCI, cystatin C also showed a significant increase in patients with CI-AKI (74.2 nmol/L IQR [65.9–118.3] vs. 70.4 nmol/L IQR [63.7–87.6]; p ⫽ 0.001). SCR and BUN plasma concentrations showed no significant differences between the two groups at this timepoint (Figures 2 and 3). The 2nd day after PCI eGFR, cystatin C, BUN as well as sCr concentrations showed significant differences between the two groups. The ROC curves of the various biomarkers 1 day after PCI for the prediction of CI-AKI within 2 days after PCI are represented in Figure 4. Urinary NGAL provided the best result with an area under the receiver-operating characteristic curve (AUC) of 0.939 (95% CI 0.89–0.99; p ⬍ 0.001). In contrast, cystatin C showed an AUC of 0.681 (95% CI 0.49–0.88; p ⫽ 0.11), sCr an AUC ⫽ 0.701 (95% CI 0.58–0.91; p ⬍ 0.01) and BUN an AUC ⫽ 0.622 (95% CI 0.38–0.86; p ⫽ 0.28). The ROC curves of uNGAL before PCI and 4 h, 1 day and 2 days after PCI for the prediction of CI-AKI within 2 days after PCI are presented in Figure 5. Urinary NGAL 1 day after PCI provided the
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C. Liebetrau et al. Table II. Laboratory measurements.
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Variable Baseline, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L) 4 hours after PCI, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L) First day after PCI, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L) Second day after PCI, median (IQR) NGAL (ng/mL) Cystatin C (nmol/L) eGFR (ml/min/1.73m2) Creatinine (μmol/L) BUN (mmol/L)
non-CI-AKI n ⫽ 114
CI-AKI n ⫽ 14
p value
11.6 68.9 87.5 77.8 6.5
(5.6–28.2) (62.2–86.9) (66.6–102.8) (68.1–91.9) (5.3–8.2)
19.8 85.4 84.4 76.0 6.7
(14.5–35.8) (65.2–119.1) (46.1–100.5) (58.3–124.6) (5.9–12.8)
0.04 0.09 0.39 0.96 0.30
7.7 68.2 91.2 72.5 6.4
(3.6–16.5) (61.4–85.4) (64.7–112.1) (64.5–88.4) (5.5–7.4)
11.0 83.1 88.3 71.6 6.9
(7.0–22.9) (64.4–125.1) (49.1–104.5) (60.1–127.3) (5.5–12.4)
0.08 0.09 0.10 0.13 0.29
16.6 70.4 86.2 80.4 6.2
(9.1–28.1) (63.7–87.6) (69.3–102.5) (68.1–90.2) (5.2–7.9)
100.1 74.2 71.4 89.3 6.6
(41.5–129.2) (65.9–118.3) (44.2–101.7) (71.6–133.5) (5.3–11.9)
⬍ 0.001 0.001 0.10 0.13 0.29
14.9 74.9 78.9 84.7 7.7
(5.9–26.9) (64.4–99.6) (58.8–97.9) (71.6–100.8) (5.3–9.0)
31.4 115.3 38.8 122.9 11.4
(21.8–57.6) (94.4–151.3) (26.9–76.1) (79.6–208.6) (8.7–15.0)
0.001 ⬍ 0.001 0.001 ⬍ 0.01 0.001
CI-AKI, contrast-induced acute kidney injury; eGFR, estimated glomerular filtration rate; NGAL, neutrophil gelatinase-associate lipocalin; PCI, percutaneous coronary intervention; BUN, blood urea nitrogen.
best result with an AUC of 0.939 (95% CI 0.89–0.99; p ⬍ 0.001). In contrast, uNGAL before PCI showed an AUC ⫽ 0.688 (95% CI 0.48–0.89; p ⫽ 0.08), and uNGAL 4 h after PCI an AUC of 0.565 (95% CI 0.37–0.77; p ⫽ 0.55), whereas uNGAL 2 days after PCI showed an AUC ⫽ 0.786 (95% CI 0.65–0.93; p ⫽ 0.008).
Cox regression analysis revealed that the risk of CI-AKI during 2 days after PCI was higher when patients were older (hazard ratio (HR) 1.12; p ⫽ 0.04) or uNGAL was increased the 1st day after PCI (HR 1.02; p ⬍ 0.001) (Table III). Surprisingly, patients with pre-existing CKD were not at higher risk for CI-AKI in our cohort.
Figure 1. Neutrophil gelatinase-associated lipocalin (NGAL) urine concentrations (median fold-change [IQR]) of all patients at baseline and throughout the study. Light-colored bars indicate patients with contrast-induced acute kidney injury (CI-AKI) and grey-colored bars indicate patients without CI-AKI.
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NGAL for CI-AKI after PCI
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Figure 2. Serum creatinine (sCR) concentrations (median fold-change [IQR]) of all patients at baseline and throughout the study. Lightcolored bars indicate patients with contrast-induced acute kidney injury (CI-AKI) and grey-colored bars indicate patients without CI-AKI.
Follow-up During the 9-months of follow-up, the re-hospitalization rate due to progressive renal insufficiency among the patients in the CI-AKI group was significantly higher (4 [28.6%] vs. 4 [3.5%], p ⬍ 0.01) than the non-CI-AKI group. NGAL concentrations the 1st day after PCI had no predictive value on re-hospitalization within 9 months.
Discussion The majority of coronary angiographies and PCI are performed as outpatient services today. Due to
the diagnostic gap of commonly used biomarkers, patients developing CI-AKI might be missed because of discharge on the day of the intervention. Therefore, the aim of the present study was to analyze whether measurement of uNGAL in the first hours after PCI predicts CI-AKI after PCI earlier and more sensitively than common biomarkers. Our study showed that uNGAL is a biomarker for the early risk stratification of CI-AKI after PCI and is superior to sCr for the early detection of CIAKI. An interesting point of our study is, that the median uNGAL concentration at baseline was significantly higher in patients developing subsequent CI-AKI, but with a large overlap between the groups
Figure 3. Blood urea nitrogen (BUN) serum concentrations (median fold-change [IQR]) of all patients at baseline and throughout the study. Light-colored bars indicate patients with contrast-induced acute kidney injury (CI-AKI) and grey-colored bars indicate patients without CI-AKI.
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C. Liebetrau et al. Table III. Hazard ratios and 95% CIs on logarithmic scale for prediction of contrast-induced acute kidney injury (CI-AKI). Variable
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age CKD Cystatin C 4 hours NGAL 4 hours eGFR first day Creatinine first day BUN first day Cystatin C first day NGAL first day
HR
CI lower
95% upper
p value
1.12 0.34 0.47 0.96 0.98 2.14 1.00 2.04 1.02
1.00 0.06 0.01 0.93 0.92 0.05 0.95 0.13 1.01
1.24 2.03 31.50 0.99 1.05 86.34 1.06 31.69 1.03
0.04 0.24 0.73 0.03 0.58 0.69 0.88 0.61 0.001
95% CI, 95% confidence interval; BUN, blood urea nitrogen; CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; HR, hazard ratio; NGAL, neutrophil gelatinaseassociated lipocalin.
Figure 4. Receiver operating characteristic (ROC) curves of the various biomarkers 1 day after PCI for the prediction of contrastinduced acute kidney injury (CI-AKI) within 2 days after PCI.
making it difficult to truly discriminate patients being at risk for CI-AKI. Nevertheless sCr, which is used in daily clinical practice, and cystatin C showed no differences between the groups at baseline. Prior studies have shown that uNGAL is a marker for minor renal injuries [15,16,21]. Patients with impaired renal function are known to be at higher risk for CI-AKI [3,6]; thus, uNGAL determination prior to PCI could indicate patients with normal sCr concentrations being at risk for CI-AKI. This is even
Figure 5. Receiver operating characteristic (ROC) curves of urinary neutrophil gelatinase-associated lipocalin (uNGAL) before percutaneous coronary intervention (PCI) and 4 h, 1 day and 2 days after PCI for the prediction of contrast-induced acute kidney injury (CI-AKI) within 2 days after PCI.
more important when patients are treated in outpatient care and worse outcomes due to missed CI-AKI might be avoided. However, this needs to be validated in a large-scale real-world scenario. Despite published data demonstrating uNGAL is a real-time marker [15,20], our data clearly demonstrate that uNGAL concentrations 4 h after elective PCI showed neither a significant difference nor increase in the CI-AKI group compared with the nonCI-AKI group. This is inconsistent with prior results, which showed uNGAL concentrations increase within 4 h after PCI [19,22,26]. The decrease of uNGAL concentrations was present in both groups and might be explainable by the hydration prior to and after PCI. Hydration status is a key factor in kidney function, urinary output, and damage, and in the development of CI-AKI. Urinary NGAL as a marker of tubular damage depends on these parameters as well. Furthermore, because of the dilution effect by hydration and/or by the contrast medium itself we could not observe any reduction of the kidney function by measuring sCR, BUN, cystatin C as well as by estimated GFR during the very early period after PCI. Because of the inaccurate definition of the exact time point of the beginning of kidney injury, the early release kinetics of uNGAL is entirely unknown. Therefore, repetitive measurements of uNGAL are required to definitely rule-out and rule-in CI-AKI. Nevertheless in patients with adequate hydration during PCI the very early measurement of uNGAL 4 h after PCI does not seem to be of value for predicting CI-AKI. The 1st day after PCI, uNGAL and cystatin C concentrations rose significantly in the CI-AKI group. In comparison to the uNGAL baseline values, the median uNGAL concentrations the 1st day after PCI were highly significant different with only few overlap between patients with and without CI-AKI allowing an adequate discrimination. Based on the AUCs of the various biomarkers, uNGAL was the strongest independent predictor of subsequent CIAKI 1 day after PCI, outperforming cystatin C and sCr. The overall increase and the total uNGAL con-
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NGAL for CI-AKI after PCI centrations were lower than expected [19,22], but still comparable to those seen in previous studies [18,26,38,31]. The higher uNGAL concentrations in other studies might be explained by comorbidities, higher amounts of contrast medium, and worse hydration statuses causing more kidney injuries and a higher overall incidence of CI-AKI. However, even with the lower increase, urinary NGAL was the most powerful predictor of CI-AKI in our study. However, regarding the hydration treatment to avoid CI-AKI further investigations are needed to determine the best time for measuring uNGAL after PCI. Clinical outcome in terms of re-hospitalization due to progressive renal insufficiency was better in patients without CI-AKI, which is consistent with the results of previous studies [5,6,9]. Contrary to other studies, uNGAL concentrations could not predict re-hospitalization in our cohort. Previously, concentrations at 6 h after contrast medium application were associated with a longer hospital stay, longer ICU stay, and higher risk for dialysis and death [28,29]. These results again confirm that uNGAL determination 4 h after PCI is not a useful time point for collecting samples. Nevertheless, regarding the follow-up data, our findings highlight the urgent necessity to treat patients at risk for CI-AKI to avoid adverse outcomes. With the higher diagnostic sensitivity of uNGAL, earlier diagnosis or maybe even prediction of CI-AKI with individual risk stratification and individualized therapy seems possible. Despite these promising results one must also remind that uNGAL is known to be elevated due to different circumstances. NGAL mRNA is normally expressed in a variety of adult human tissues, including bone marrow, uterus, prostate, salivary gland, stomach, colon, trachea, lung, liver and kidney [33]. In this context it is also known to be elevated in a number of human cancers, where it often represents a predictor of poor prognosis [34]. In addition, uNGAL is a part of the innate immune response due to bacterial infection and it acts also as a growth factor. Therefore of the increase of NGAL concentrations might not always be due to renal impairment. Decavale et al. could show this uNGAL increase in case of leucocyturia [35]. CI-AKI might therefore be more difficult to detect in case of systemic inflammation. This might especially be of interest in patients presenting with acute coronary syndrome. Urinary NGAL concentrations might be false positive in those patients due to the inflammatory response in case of acute myocardial infarction. To exclude false positive results for example leucocytes in urine and blood should be determined in addition to uNGAL. The results of our study should be interpreted in the context of several limitations. The laboratory results of conventional biomarkers like sCR and/or BUN in previous studies as well as in our study show a very low diagnostic sensitivity in terms of CI-AKI detection, but provide insight in daily clinical practice.
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The small number of enrolled consecutive patients from a single center is a major limitation of our study that must be considered. Due to the study size the number of events could be too low to draw definitive conclusions. Nevertheless the data are sufficient to demonstrate a significant increase in uNGAL concentrations with superiority to the conventional biomarkers the 1st day after PCI. Therefore further clinical investigations are necessary to determine firstly the best time point for uNGAL measurement after PCI if patients are hydrated sufficiently and secondly how CI-AKI might be avoided by preventive treatment. Conclusion Urinary NGAL is a biomarker for early risk stratification of CI-AKI after PCI. It may be able to predict CI-AKI prior to contrast medium application. However, it is not a real-time marker for CI-AKI after PCI. Prospective studies are needed to investigate whether uNGAL concentrations could be used as the basis for prophylactic or early interventional strategies to prevent CI-AKI after PCI. Acknowledgements Abbott Diagnostics donated urinary NGAL and cystatin C assays. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. The funding sources were not involved in the design of the trial, the gathering, analysis and interpretation of data, the writing of the manuscript or the decision to publish the paper.
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Notice of correction The online version of this article published ahead of print on 5 Dec 2013 contained an error on page 6. The same image was published twice in figures 4 and 5. The error has been corrected for this version.
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