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Nephrology 20 (2015) 881–886
Original Article
Optimum methodology for estimating baseline serum creatinine for the acute kidney injury classification CHARAT THONGPRAYOON,1 WISIT CHEUNGPASITPORN,1 WONNGARM KITTANAMONGKOLCHAI,1 NARAT SRIVALI,2 PATOMPONG UNGPRASERT3 and KIANOUSH KASHANI1,2 Divisions of 1Nephrology and Hypertension and 2Pulmonary and Critical Care Medicine and 3Rheumatology, Mayo Clinic, Rochester, Minnesota, USA
KEY WORDS: acute renal failure (ARF), acute tubular necrosis (ATN), glomerular filtration rate (GFR). Correspondence: Dr Charat Thongprayoon, Division of Nephrology and Hypertension, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. Email: [email protected] Financial support: None. Conflicts of interest: None.
Accepted for publication 25 May 2015. Accepted manuscript online 1 June 2015. doi:10.1111/nep.12525
SUMMARY AT A GLANCE This manuscript suggests that rather than the most recent serum creatinine, using the minimum preadmission serum cretainine value allows more accurate identification of patients with acute kidney injury at risk of adverse outcomes.
ABSTRACT: Aim: This study aimed to investigate how varied methods of determining baseline serum creatinine (SCr) would affect acute kidney injury (AKI) diagnosis and prediction of 60 day mortality in critically ill patients following an episode of AKI. Methods: This is a single-centre retrospective study conducted at a tertiary referral hospital. All adult intensive care unit (ICU) patients between January and December 2011, who had at least one SCr values measured between 7 days and 180 days before hospital admission and during ICU stay, were analyzed. The baseline SCr was calculated using either the most recent (SCrmost recent) or the minimum (SCrmin) value of SCr measurement over the specified assessment period before hospital admission. AKI was defined based on KDIGO SCr definition. The primary outcome was 60 day mortality after ICU admission. Results: A total of 4020 patients were included in the analysis. AKI was detected in 1204 (30.0%) using the SCrmin and 945 (23.5%) using the SCrmost recent (P < 0.001). Compared with patients without AKI regardless of baseline SCr methodology, the 60 day mortality risk of patients who developed AKI using the SCrmin and SCrmost recent was significantly increased (odds ratio (OR) = 3.74; 95% confidence interval (CI) 2.98–4.70). Similarly, the risk of 60 day mortality in patients who met AKI criteria using the SCrmin but not the SCrmost recent was significant higher than in patients without AKI (OR = 2.04; 95% CI 1.36–3.00). Conclusion: Using the minimum value of preadmission SCr as a baseline kidney function not only can detect more AKI cases, but also provides the better predictive ability for 60 day mortality.
Acute kidney injury (AKI) is increasingly prevalent in critically ill patients and is independently associated with increased mortality, morbidity and resource utilization.1–6 In some reports, up to 45% of patients admitted to intensive care units (ICU) and 20% of hospitalized patients experienced AKI.7,8 Kidney Disease: Improving Global Outcomes (KDIGO) criteria was developed and validated to standardize the diagnosis and disease severity of AKI based on absolute or relative increases in serum creatinine (SCr) and progressive degree of oliguria.9 Accordingly, determination of baseline SCr is very important in AKI diagnosis and classification. Inaccurate determination of baseline SCr can misclassify AKI and sub© 2015 Asian Pacific Society of Nephrology
sequently affect the prognostication of AKI-related outcomes.10,11 Studies have shown that outpatient SCr is a more robust assessment of baseline renal function than inpatient SCr, because it represents a steady state and is not altered by the index critical illness.12 However, there is currently no consensus on how to optimally determine baseline SCr when multiple preadmission SCr measurements are available, leading to heterogeneity across research studies.13,14 This study aimed to investigate how varied methods of determining baseline SCr in AKI diagnosis would affect the time of diagnosis, staging of AKI and prediction of 60 day mortality in critically ill patients following an episode of AKI. 881
C Thongprayoon et al.
MATERIALS AND METHODS Study population This was a single-centre, retrospective study conducted at a tertiary referral hospital. We studied all adult patients (age ≥18 years) admitted to the ICUs at Mayo Clinic Hospital, Rochester, MN, from 1 January to 31 December 2011. We included patients who had at least one SCr measured in ICU and at least one SCr measured between 7 and 180 days prior to the index ICU admission. Patients with a history of stage 5 chronic kidney disease (CKD) or end-stage renal disease (ESRD), patients who received any dialysis modalities within 14 days prior to the ICU admission and patients who did not provide research authorization were excluded from the study. Stage 5 CKD and ESRD diseases were identified based on The International Classification of Diseases, Ninth Revision (ICD-9) code assignment (Table S1), or baseline SCr-calculated estimated glomerular filtration rate (eGFR) of
Nephrology 20 (2015) 881–886
Original Article
Optimum methodology for estimating baseline serum creatinine for the acute kidney injury classification CHARAT THONGPRAYOON,1 WISIT CHEUNGPASITPORN,1 WONNGARM KITTANAMONGKOLCHAI,1 NARAT SRIVALI,2 PATOMPONG UNGPRASERT3 and KIANOUSH KASHANI1,2 Divisions of 1Nephrology and Hypertension and 2Pulmonary and Critical Care Medicine and 3Rheumatology, Mayo Clinic, Rochester, Minnesota, USA
KEY WORDS: acute renal failure (ARF), acute tubular necrosis (ATN), glomerular filtration rate (GFR). Correspondence: Dr Charat Thongprayoon, Division of Nephrology and Hypertension, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. Email: [email protected] Financial support: None. Conflicts of interest: None.
Accepted for publication 25 May 2015. Accepted manuscript online 1 June 2015. doi:10.1111/nep.12525
SUMMARY AT A GLANCE This manuscript suggests that rather than the most recent serum creatinine, using the minimum preadmission serum cretainine value allows more accurate identification of patients with acute kidney injury at risk of adverse outcomes.
ABSTRACT: Aim: This study aimed to investigate how varied methods of determining baseline serum creatinine (SCr) would affect acute kidney injury (AKI) diagnosis and prediction of 60 day mortality in critically ill patients following an episode of AKI. Methods: This is a single-centre retrospective study conducted at a tertiary referral hospital. All adult intensive care unit (ICU) patients between January and December 2011, who had at least one SCr values measured between 7 days and 180 days before hospital admission and during ICU stay, were analyzed. The baseline SCr was calculated using either the most recent (SCrmost recent) or the minimum (SCrmin) value of SCr measurement over the specified assessment period before hospital admission. AKI was defined based on KDIGO SCr definition. The primary outcome was 60 day mortality after ICU admission. Results: A total of 4020 patients were included in the analysis. AKI was detected in 1204 (30.0%) using the SCrmin and 945 (23.5%) using the SCrmost recent (P < 0.001). Compared with patients without AKI regardless of baseline SCr methodology, the 60 day mortality risk of patients who developed AKI using the SCrmin and SCrmost recent was significantly increased (odds ratio (OR) = 3.74; 95% confidence interval (CI) 2.98–4.70). Similarly, the risk of 60 day mortality in patients who met AKI criteria using the SCrmin but not the SCrmost recent was significant higher than in patients without AKI (OR = 2.04; 95% CI 1.36–3.00). Conclusion: Using the minimum value of preadmission SCr as a baseline kidney function not only can detect more AKI cases, but also provides the better predictive ability for 60 day mortality.
Acute kidney injury (AKI) is increasingly prevalent in critically ill patients and is independently associated with increased mortality, morbidity and resource utilization.1–6 In some reports, up to 45% of patients admitted to intensive care units (ICU) and 20% of hospitalized patients experienced AKI.7,8 Kidney Disease: Improving Global Outcomes (KDIGO) criteria was developed and validated to standardize the diagnosis and disease severity of AKI based on absolute or relative increases in serum creatinine (SCr) and progressive degree of oliguria.9 Accordingly, determination of baseline SCr is very important in AKI diagnosis and classification. Inaccurate determination of baseline SCr can misclassify AKI and sub© 2015 Asian Pacific Society of Nephrology
sequently affect the prognostication of AKI-related outcomes.10,11 Studies have shown that outpatient SCr is a more robust assessment of baseline renal function than inpatient SCr, because it represents a steady state and is not altered by the index critical illness.12 However, there is currently no consensus on how to optimally determine baseline SCr when multiple preadmission SCr measurements are available, leading to heterogeneity across research studies.13,14 This study aimed to investigate how varied methods of determining baseline SCr in AKI diagnosis would affect the time of diagnosis, staging of AKI and prediction of 60 day mortality in critically ill patients following an episode of AKI. 881
C Thongprayoon et al.
MATERIALS AND METHODS Study population This was a single-centre, retrospective study conducted at a tertiary referral hospital. We studied all adult patients (age ≥18 years) admitted to the ICUs at Mayo Clinic Hospital, Rochester, MN, from 1 January to 31 December 2011. We included patients who had at least one SCr measured in ICU and at least one SCr measured between 7 and 180 days prior to the index ICU admission. Patients with a history of stage 5 chronic kidney disease (CKD) or end-stage renal disease (ESRD), patients who received any dialysis modalities within 14 days prior to the ICU admission and patients who did not provide research authorization were excluded from the study. Stage 5 CKD and ESRD diseases were identified based on The International Classification of Diseases, Ninth Revision (ICD-9) code assignment (Table S1), or baseline SCr-calculated estimated glomerular filtration rate (eGFR) of
