The Clinical Respiratory Journal
ORIGINAL ARTICLE
Correlation between the Wells score and the Quanadli index in patients with pulmonary embolism Dušanka Obradovic´1,2, Biljana Joveš1,2, Slobodanka Pena Karan1,2, Srdjan Stefanovic´1,2, Igor Ivanov2,3 and Marija Vukoja1,2 1 Institute for Pulmonary Diseases of Vojvodina, Sremska Kamenica, Serbia 2 Medical Faculty Novi Sad, University of Novi Sad, Novi Sad, Serbia 3 Institute for Cardiovascular Diseases of Vojvodina, Sremska Kamenica, Serbia
Abstract Background and Aims: Determining clinical probability of pulmonary embolism (PE) with Wells scoring system is the first step towards diagnosis of PE. Definitive diagnosis of PE is confirmed by computed tomography pulmonary angiography (CTPA). Methods: This was a prospective study on 80 patients referred to the Institute for Pulmonary Diseases of Vojvodina with suspected PE between April 2010 and August 2012. Clinical probability of PE was determined according to the Wells and modified Wells scoring system. CTPA was performed in 60 patients. The degree of pulmonary vascular obstruction was quantified by the Qanadli index. Results: Low clinical probability of PE was present in one patient (1.6%), moderate in 43 (71.6%) and high in 16 (26.6%) patients. PE was confirmed in 50 (83.3%) patients. There were 21 patients (42%) whose Quanadli index was 6 ≤4 >4
PE, pulmonary embolism.
The Clinical Respiratory Journal (2015) • ISSN 1752-6981 © 2015 John Wiley & Sons Ltd
Obradovic´ et al.
includes topogram and native series, as well as data acquisition during the contrast phase (12). Patients were scanned in the supine position. The total of 80–120 mL non-ionic radiocontrast agent of 350–370 i.u. concentration was applied intravenously, with the addition of 40 mL–80 mL saline. The contrast was delivered with the Covidien automatic dualhead injector Optivantage DH (Mallinckrodt plc, Damastown, Mulhuddart, Dublin 15, Ireland). The contrast flow was set at 4,5 mL/min, in accordance with the protocol. Starting acquisition time of the postcontrast phase was determined with the low-dose scanning of pulmonary artery in 1-s intervals, with ‘smart preparation’ programme. X-ray tube voltage was 120 kV, and the anode current strength was automatically corrected according to the width of the examined body section, by ‘autom A’ application. Data collected through the volume acquisition were shown as the axial 1.25 mm collimation multislice computed tomography scans, multiplanar reconstructions, maximal intensity projection, minimal intensity projection and volume rendering techniques. Scan processing was performed in the General Electric (GE) workstation, Advantage 4.4 (GE Healthcare Clinical Systems, Hatfield, Herts, UK). The degree of vascular obstruction was quantified with the Quanadli index (13), according to the following formula : Σ(n × d)/40 × 100, in which: n represents the number of pulmonal artery segmental branches with thrombi (minimum 1, maximum 20 – each lung has 10 segmental branches – three for the upper lobe, two for the middle lobe and lingula and five for the lower lobe). d represents the degree of obstruction (1 if there is a flow distal to the thrombus or 2 if there is a complete obstruction). All the patients in our research were scanned by spiral or 64-slice GE scanner – both native and after intravenous application of the radiocontrast agent. SPSS v.17 software (SPSS Inc, Chicago, IL, USA) for Windows was used for statistical analysis of the collected data. Descriptive statistics included frequency analysis (percentages) for categorical variables and means and standard deviations (SDs) or medians and interquartile ranges for continuous variables. To test for difference in characteristics between two or more groups, we used relevant parametric (Student’s t-test, ANOVA) and non-parametric tests (Chi-square test, Fisher’s exact test). Pearson correlation coefficient was used to measure linear correlation between two variables. We considered P values of 4), there were 53 patients (88.3%). PE was confirmed in 45 of these patients (84.9%) (Table 3). When tested against CTPA findings, modified Wells score had 90.00% sensitivity (95% CI 78.2%–96.6%), while specificity was 20% (95% CI 3.11%–55.6%), PPV 84.9% (95% CI 72.4%–93.2%) and NPV 28.6% (95% CI 4.5%–70.7%). CTPA was performed between 0–8 day upon hospital admission for suspected PE, mean interval between the suspected PE and CTPA was 4.06 days. There were two reasons for this delay in diagnostics – one is technical in nature, since 15 patients were admitted to hospital during the weekend, when CTPA was not available, and the other reason is clinical – 15 patients were haemodynamically unstable, and CTPA was performed after haemodynamic stabilization.
Table 2. Baseline characteristics of the examined patients
Sex n (%) Age, mean (range)
CTPA Positive n = 50
CTPA Negative n = 10
P Value
27 male (54) 51.04 (23–77)
6 male (60) 51.80 (24–71)
1.000 0.889
CTPA, computed tomography pulmonary angiography.
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Table 3. Classification of patients with suspected PE according to clinical probability estimated by the Wells and modified Wells score and CTPA findings Clinical Probability of PE (the Wells and Modified Wells)
CTPA Positive Finding n = 50 (83.33%)
Negative Finding n = 10 (26.67%)
Total n = 60
Low (0–1) Intermediate (2–6) High (>6) Low ≤4 High (>4)
1 (100%) 33 (76.74%) 16 (100%) 5 (71.43) 45 (84.90%)
0 10 (23.26%) 0 2 (28.57)0 8 (15.10%)
1 (100%) 43 (100%) 16 (100%) 7 (100%) 53 (100%)
CTPA, computed tomography pulmonary angiography; PE, pulmonary embolism.
The Quanadli index of pulmonary vessels obstruction was calculated for all patients. Mean value of the obstruction index was 23.38% (SD ±17.61). We divided all the patients based on their Quanadli index in three and then in two groups: I group with Quanadli index 0%–25%, II group with Quanadli index 25%– 50%, III group with Quanadli index of over 50%, and then I group with Quanadli index 0%–50% and II group with Quanadli index of over 50%. In the group with Quanadli index of up to 25% (I group), there were 21 patients (42%), in the second group with Quanadli of 25%–50%, there were 18 patients (36%), and in the group III there were 11 patients (22%). Quanadli index was labeled zero in the patients in whom PE was excluded by CTPA. Mean value of the Wells score in group I was 5.56, in group II was 5.91, while this value was the highest in group III – 6.23. There was no statistically significant difference between mean values of Wells and the degree of pulmonary vessels obstruction estimated with the Quanadli index (ANOVA, F = 0.636, P = 0.533) (Table 4). There was a weak positive correlation between the Wells score and the Quanadli index, but it was not statistically significant (r = 0.14; P = 0.289). One patient who had a low clinical probability of PE (Wells 1.5 assigned for sinus tachycardia) developed
Table 4. Mean values of the Wells score and the Quanadli index Wells Score Quanadli No. of Standard Index Patients Mean Deviation Minimum Maximum I group II group III group Total
4
21 18 11 60
5.56 5.92 6.27 5.80
1.67 2.21 1.77 1.85
3.0 1.5 4.5 1.5
9.0 10.5 10.0 10.5
clinical signs of right calf deep venous thrombosis after 7 days, which was then confirmed by ultrasound and CTPA. There was a total of 15 high-risk patients (haemodynamic instability with systolic blood pressure of ≤90 mmHg at admission) who received thrombolytic therapy. All 15 patients survived. In these patients, CTPA was performed after haemodynamic stabilization and thrombolytic therapy. Decision on thrombolytic therapy was made after transthoracic echocardiography within 30 min upon admission and verification of echocardiographic signs of acute right ventricular dysfunction. There were nine female (60%) and six male (40%) patients in this group where mean age was 50 (23–75 years of age). According to the Wells score, there were seven patients (46.66%) with high clinical probability of PE in this group (two patients had 7.5 points, four patients had 9 points, and one patient had 10 points). The rest had intermediate clinical probability of PE (four patients had 4.5 points, three patients had 6 points, and one patient had 5 points). We compared mean values of the Wells score in two groups: haemodynamically unstable and haemodynamically stable patients with PE (Table 5). Haemodynamically unstable patients had significantly higher mean Wells score (6.8 to 5.6, P = 0.014). We compared mean values of the Wells score in haemodynamically unstable patients with PE and the patients in which PE was excluded by CTPA (Table 6). Mean value of the Wells score was significantly higher in haemodynamically unstable patients (6.8 to 4.8), P = 0.008). We made a correlation between the Quanadli index of obstruction in haemodynamically unstable and haemodynamically stable patients (Table 7). There was a higher mean value of the Quanadli index in the haemodynamically unstable group, but
The Clinical Respiratory Journal (2015) • ISSN 1752-6981 © 2015 John Wiley & Sons Ltd
Obradovic´ et al.
Correlation between Wells and Quanadli in PE
Table 5. Mean values of the Wells score in haemodynamically unstable and haemodynamically stable patients Wells score n Haemodynamically Unstable Haemodynamically Stable Total
Maximum
2.02
4.5
10.0
15 35
5.656
1.81
1.5
10.5
50
6.00
1.93
1.5
10.5
Discussion Diagnosing pulmonary embolism still poses a challenge to clinicians, in spite of all the available modern diagnostic procedures. Based on the autopsy findings, diagnosis of PE is missed in up to 30%–50% of patients (14). It is not possible to diagnose PE based only on symptoms and clinical signs, since the sole clinical evaluation is insufficient to confirm or exclude PE. In our study, we used the Wells scoring system and the modified Wells scoring system to determine clinical probability of PE. In PIOPED trial (3) prevalence of PE was 9% in patients classified as having low clinical probability of PE, and 30% in the group of patients with intermediate probability of PE, while prevalence Table 6. Mean values of the Wells score in haemodynamically unstable patients with pulmonary embolism (PE) and the patients in which PE was excluded Wells score
X 6.80
SD
Minimum
Maximum
15
2.02
4.5
10.0
10 25
4.80 6.00
0.95 1.93
3.0 3.0
6.0 10.0
N
Minimum
X 6.80
the difference did not bear statistical significance (31.33% to 26.64%, P = 0.062).
Hemodynamically unstable PE excluded Total
Standard Deviation
was 68% in the group with high clinical probability of PE. Our results are different, most probably because of the fact that overall prevalence in our patients was 83.33% (100% in patients classified as having low clinical probability of PE, 76.64% in the group of patients with intermediate probability of PE and 100% in the group with high probability of PE). Mohammad et al. (4) did a study which included 99 patients, and they also used the Wells scoring system to determine clinical probability of PE. There were eight patients (8.1%) in the group with low clinical probability of PE, 68 (68.7%) were classified as having intermediate clinical probability and 23.3% as having high clinical probability. In this study, PE was confirmed in 68% of patients whose Wells score was between 2–6 points, and in 90% of patients whose Wells score was >6 points. In our study, PE was confirmed in 33 out of 43 patients (prevalence of PE 76.74%) in the group with Wells score of 2–6 points, and PE was confirmed in all 16 patients with Wells score of >6 points (prevalence 100%). These findings confirm that the higher Wells score, the higher prevalence of PE (7, 15). Diversity of data cited in the above-mentioned studies can be explained by different prevalence of PE in general. Unfortunately, we have no valid data on PE prevalence in our country; therefore, the Wells scoring system was elected according to the results of Ceriani et al. meta-analysis (7) that recommended either Wells (10) or Miniati scoring system (16) for hospitalized patients.
Table 7. Mean values of the Quanadli index of obstruction in haemodynamically unstable and haemodynamically stable patients Quanadli index (%)
X 31.33
SD
Minimum
Maximum
15
16.34
2.5
50.0
35 50
26.64 28.05
15.12 15.47
5.0 2.5
55.0 55.0
n Haemodynamically unstable Haemodynamically stable Total
The Clinical Respiratory Journal (2015) • ISSN 1752-6981 © 2015 John Wiley & Sons Ltd
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Correlation between Wells and Quanadli in PE
One retrospective observational research (17) included 286 hospitalized patients with suspected PE (patients had previously received prophylactic doses of heparin), and PE was confirmed in 57 patients (20%). There was 95% sensitivity in this group, and 27% specificity, 27%, PPV 9% and NPV 99% for modified Wells criteria, which is in line with our results. However, our research has shown a high PPV, since the prevalence of PE was much higher in our group of patients (83.33%). One prospective trial included 613 patients (18) with suspected PE during their hospitalization, and the diagnosis was confirmed in 36% patients. Of these patients 394 (66%) were classified as having low clinical probability of PE, according to the modified Wells score, and 219 patients (34%) were classified as having high clinical probability of PE. The modified Wells criteria yielded sensitivity of 65%, specificity of 81%, PPV was 66% and NPV was 80%. Our results for NPV are different, since prevalence of PE in patients with low clinical probability was over 70%. The Quanadli index estimates the degree of pulmonary blood vessels obstruction in PE as visualised by CTPA (13). Quanadli index has proven simple to calculate, reproducible and adequate to quantify PE. In our study, there was no statistically significant correlation between the Wells score values and the degree of obstruction estimated by Quanadli index. Mean Wells score was the highest in the group of patients with Quanadli index higher than 50%, but we have not been able to show statistical significance of this correlation. According to Rodrigues et al. (19), there is a statistically significant correlation between higher values of the Wells score and higher values of the Quanadli index; however, this trial excluded patients with low clinical probability of PE. The study from Turkey (20) also showed statistically significant correlation between the values of Wells score and the degree of pulmonary vessels obstruction evaluated by CTPA (r = 0.470, P < 0.001). In our research, there was no statistically significant difference between mean values of the Wells score and the degree of obstruction estimated by the Quanadli index (ANOVA, F = 0.636, P = 0.533), and there was a weak correlation between the values of the Wells score and the Quanadli index, which was not statistically significant (r = 0.14; P = 0.289). According to our results, the Wells score does not predict the degree of pulmonary obstruction in patients with PE. On the other hand, our results show statistically significant higher value of the Wells score in patients with haemodynamically unstable PE compared to haemodynamically stable patients and
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Obradovic´ et al.
patients in whom PE was excluded. Also, mean Quanadli index was higher in the group of patients with haemodynamically unstable PE than in the group with haemodynamically stable PE, but there was no statistical significance. Mean value for the obstruction index in our haemodynamically unstable patients was 31.33%, while the colleagues from Turkey found this index to be 52.9% in haemodynamically unstable patients. A possible explanation is that in our study CTPA and Quanadli indexing followed thrombolytic therapy and haemodynamic stabilization. Another limitation of our study is that CTPA was performed on average of 4 days after the admission when the patients had already received either anticoagulants or thrombolytics. This suggests that the relationship between the degree of clinical probability of PE and the degree of pulmonary vascular obstruction is largely time dependent.
Conclusion In our study, modified Wells criteria had high sensitivity but low specificity in PE diagnostics. There was no significant correlation between the degree of clinical probability of PE and the degree of pulmonary vascular obstruction, which may be because of the delayed CTPA diagnostic in some patients.
References 1. Karwinski B, Sendesn E. Comparison of clinical and postmortem diagnosis of pulmonary embolism. J Clin Pathol. 1989;42: 135–9. 2. Torbicki A, Perrier A, Konstantinides S, et al. Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary embolism of the European Society of Cardiology (ESC). Eur Heart J. 2008;29: 2276–315. 3. The PIOPED Investigators. Value of the ventilation/perfusion scan in acute pulmonary embolism. Results of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). JAMA. 1990;263: 2753–9. 4. Mohammad MM, Adimi P, Seyedi SR, Kashani B. Assessment of Wells criteria in patients with pulmonary embolism. Tanaffos. 2008;7(2): 50–3. 5. Musset D, Parent F, Meyer G, et al. Diagnostic strategy for patients with suspected pulmonary embolism: a prospective multicentre outcome trial. Lancet. 2002;360: 1914–20. 6. Perrier A, Miron MJ, Desmarais S, et al. Using clinical evaluation and lung scan to rule out suspected pulmonary embolism: is it a valid option in patients with normal
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results of lower-limb venous compression ultrasonography? Arch Intern Med. 2000;160: 512–6. Ceriani E, Combescure C, Le Gal G, et al. Clinical prediction rules for pulmonary embolism: a systematic review and meta analysis. J Thromb Haemost. 2010;8: 957–70. McGinn TG, Guyatt GH, Wyer PC, Naylor CD, Stiell IG, Richardson WS, Evidence-Based Medicine Working Group. Users’ guides to the medical literature: XXII: how to use articles about clinical decision rules. JAMA. 2000;284: 79–84. Stein PD, Fowler SE, Goodman LR, et al. Multidetector computed tomography for acute pulmonary embolism. N Engl J Med. 2006;354(22): 2317–27. Wells PS, Ginsberg JS, Anderson DR, et al. Use of a clinical model for safe management of patients with suspected pulmonary embolism. Ann Intern Med. 1998;129: 997–1005. Gibson NS, Sohne M, Kruip MJ, et al. Further validation and simplification of the Wells clinical decision rule in pulmonary embolism. Thromb Haemost. 2008;99: 229–34. Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation; Board on Radiation Effects Research; Division on Earth and Life Studies; National Research Council. Health risks from exposure to low level of ionizing radiation:BEIR VII, phase 2, 2006. Quanadli SD, El Hajjam M, Vieillard-Baron A, et al. New CT index to quantify arterial obstruction in pulmonary embolism: a comparison with angiographic index and
The Clinical Respiratory Journal (2015) • ISSN 1752-6981 © 2015 John Wiley & Sons Ltd
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echocardiography. AJR Am J Roentgenol. 2001;176(6): 1415–1420. White RH. The epidemiology of venous thromboembolism. Circulation. 2003;107(Suppl. 1): I4–8. Hoellerich VL, Wigton RS. Diagnosing pulmonary embolism using clinical findings. Arch Intern Med. 1986;146: 1699–704. Miniati M, Prediletto R, Formichi B, et al. Accuracy of clinical assessment in the diagnosis of pulmonary embolism. Am J Respir Crit Care Med. 1999;159: 864–71. Bahia A, Albert RK. The modified Wells score accurately excludes pulmonary embolus in hospitalized patients receiving heparin prophylaxis. J Hosp Med. 2011;6(4): 190–4. Posadas-Martínez ML, Vázquez FJ, Giunta DH, Waisman GD, de Quirós FG, Gándara E. Performance of the Wells score in patients with suspected pulmonary embolism during hospitalization: a delayed-type cross sectional trial in a community hospital. Thromb Res. 2014;133(2): 177–81. Rodrigues B. O valor da carga embólica na avaliação de disfunção ventricular direita no tromboembolismo pulmonar agudo: quantificando a causae clarificando as consequências. Rev Port Cardiol. 2012;31: 687–95. I˙nönü H, Acu B, Pazarli AC, et al. The value of the computed tomographic obstruction index in the identification of massive pulmonary thromboembolism. Diagn Interv Radiol. 2012;18: 255–60.
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ORIGINAL ARTICLE
Correlation between the Wells score and the Quanadli index in patients with pulmonary embolism Dušanka Obradovic´1,2, Biljana Joveš1,2, Slobodanka Pena Karan1,2, Srdjan Stefanovic´1,2, Igor Ivanov2,3 and Marija Vukoja1,2 1 Institute for Pulmonary Diseases of Vojvodina, Sremska Kamenica, Serbia 2 Medical Faculty Novi Sad, University of Novi Sad, Novi Sad, Serbia 3 Institute for Cardiovascular Diseases of Vojvodina, Sremska Kamenica, Serbia
Abstract Background and Aims: Determining clinical probability of pulmonary embolism (PE) with Wells scoring system is the first step towards diagnosis of PE. Definitive diagnosis of PE is confirmed by computed tomography pulmonary angiography (CTPA). Methods: This was a prospective study on 80 patients referred to the Institute for Pulmonary Diseases of Vojvodina with suspected PE between April 2010 and August 2012. Clinical probability of PE was determined according to the Wells and modified Wells scoring system. CTPA was performed in 60 patients. The degree of pulmonary vascular obstruction was quantified by the Qanadli index. Results: Low clinical probability of PE was present in one patient (1.6%), moderate in 43 (71.6%) and high in 16 (26.6%) patients. PE was confirmed in 50 (83.3%) patients. There were 21 patients (42%) whose Quanadli index was 6 ≤4 >4
PE, pulmonary embolism.
The Clinical Respiratory Journal (2015) • ISSN 1752-6981 © 2015 John Wiley & Sons Ltd
Obradovic´ et al.
includes topogram and native series, as well as data acquisition during the contrast phase (12). Patients were scanned in the supine position. The total of 80–120 mL non-ionic radiocontrast agent of 350–370 i.u. concentration was applied intravenously, with the addition of 40 mL–80 mL saline. The contrast was delivered with the Covidien automatic dualhead injector Optivantage DH (Mallinckrodt plc, Damastown, Mulhuddart, Dublin 15, Ireland). The contrast flow was set at 4,5 mL/min, in accordance with the protocol. Starting acquisition time of the postcontrast phase was determined with the low-dose scanning of pulmonary artery in 1-s intervals, with ‘smart preparation’ programme. X-ray tube voltage was 120 kV, and the anode current strength was automatically corrected according to the width of the examined body section, by ‘autom A’ application. Data collected through the volume acquisition were shown as the axial 1.25 mm collimation multislice computed tomography scans, multiplanar reconstructions, maximal intensity projection, minimal intensity projection and volume rendering techniques. Scan processing was performed in the General Electric (GE) workstation, Advantage 4.4 (GE Healthcare Clinical Systems, Hatfield, Herts, UK). The degree of vascular obstruction was quantified with the Quanadli index (13), according to the following formula : Σ(n × d)/40 × 100, in which: n represents the number of pulmonal artery segmental branches with thrombi (minimum 1, maximum 20 – each lung has 10 segmental branches – three for the upper lobe, two for the middle lobe and lingula and five for the lower lobe). d represents the degree of obstruction (1 if there is a flow distal to the thrombus or 2 if there is a complete obstruction). All the patients in our research were scanned by spiral or 64-slice GE scanner – both native and after intravenous application of the radiocontrast agent. SPSS v.17 software (SPSS Inc, Chicago, IL, USA) for Windows was used for statistical analysis of the collected data. Descriptive statistics included frequency analysis (percentages) for categorical variables and means and standard deviations (SDs) or medians and interquartile ranges for continuous variables. To test for difference in characteristics between two or more groups, we used relevant parametric (Student’s t-test, ANOVA) and non-parametric tests (Chi-square test, Fisher’s exact test). Pearson correlation coefficient was used to measure linear correlation between two variables. We considered P values of 4), there were 53 patients (88.3%). PE was confirmed in 45 of these patients (84.9%) (Table 3). When tested against CTPA findings, modified Wells score had 90.00% sensitivity (95% CI 78.2%–96.6%), while specificity was 20% (95% CI 3.11%–55.6%), PPV 84.9% (95% CI 72.4%–93.2%) and NPV 28.6% (95% CI 4.5%–70.7%). CTPA was performed between 0–8 day upon hospital admission for suspected PE, mean interval between the suspected PE and CTPA was 4.06 days. There were two reasons for this delay in diagnostics – one is technical in nature, since 15 patients were admitted to hospital during the weekend, when CTPA was not available, and the other reason is clinical – 15 patients were haemodynamically unstable, and CTPA was performed after haemodynamic stabilization.
Table 2. Baseline characteristics of the examined patients
Sex n (%) Age, mean (range)
CTPA Positive n = 50
CTPA Negative n = 10
P Value
27 male (54) 51.04 (23–77)
6 male (60) 51.80 (24–71)
1.000 0.889
CTPA, computed tomography pulmonary angiography.
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Table 3. Classification of patients with suspected PE according to clinical probability estimated by the Wells and modified Wells score and CTPA findings Clinical Probability of PE (the Wells and Modified Wells)
CTPA Positive Finding n = 50 (83.33%)
Negative Finding n = 10 (26.67%)
Total n = 60
Low (0–1) Intermediate (2–6) High (>6) Low ≤4 High (>4)
1 (100%) 33 (76.74%) 16 (100%) 5 (71.43) 45 (84.90%)
0 10 (23.26%) 0 2 (28.57)0 8 (15.10%)
1 (100%) 43 (100%) 16 (100%) 7 (100%) 53 (100%)
CTPA, computed tomography pulmonary angiography; PE, pulmonary embolism.
The Quanadli index of pulmonary vessels obstruction was calculated for all patients. Mean value of the obstruction index was 23.38% (SD ±17.61). We divided all the patients based on their Quanadli index in three and then in two groups: I group with Quanadli index 0%–25%, II group with Quanadli index 25%– 50%, III group with Quanadli index of over 50%, and then I group with Quanadli index 0%–50% and II group with Quanadli index of over 50%. In the group with Quanadli index of up to 25% (I group), there were 21 patients (42%), in the second group with Quanadli of 25%–50%, there were 18 patients (36%), and in the group III there were 11 patients (22%). Quanadli index was labeled zero in the patients in whom PE was excluded by CTPA. Mean value of the Wells score in group I was 5.56, in group II was 5.91, while this value was the highest in group III – 6.23. There was no statistically significant difference between mean values of Wells and the degree of pulmonary vessels obstruction estimated with the Quanadli index (ANOVA, F = 0.636, P = 0.533) (Table 4). There was a weak positive correlation between the Wells score and the Quanadli index, but it was not statistically significant (r = 0.14; P = 0.289). One patient who had a low clinical probability of PE (Wells 1.5 assigned for sinus tachycardia) developed
Table 4. Mean values of the Wells score and the Quanadli index Wells Score Quanadli No. of Standard Index Patients Mean Deviation Minimum Maximum I group II group III group Total
4
21 18 11 60
5.56 5.92 6.27 5.80
1.67 2.21 1.77 1.85
3.0 1.5 4.5 1.5
9.0 10.5 10.0 10.5
clinical signs of right calf deep venous thrombosis after 7 days, which was then confirmed by ultrasound and CTPA. There was a total of 15 high-risk patients (haemodynamic instability with systolic blood pressure of ≤90 mmHg at admission) who received thrombolytic therapy. All 15 patients survived. In these patients, CTPA was performed after haemodynamic stabilization and thrombolytic therapy. Decision on thrombolytic therapy was made after transthoracic echocardiography within 30 min upon admission and verification of echocardiographic signs of acute right ventricular dysfunction. There were nine female (60%) and six male (40%) patients in this group where mean age was 50 (23–75 years of age). According to the Wells score, there were seven patients (46.66%) with high clinical probability of PE in this group (two patients had 7.5 points, four patients had 9 points, and one patient had 10 points). The rest had intermediate clinical probability of PE (four patients had 4.5 points, three patients had 6 points, and one patient had 5 points). We compared mean values of the Wells score in two groups: haemodynamically unstable and haemodynamically stable patients with PE (Table 5). Haemodynamically unstable patients had significantly higher mean Wells score (6.8 to 5.6, P = 0.014). We compared mean values of the Wells score in haemodynamically unstable patients with PE and the patients in which PE was excluded by CTPA (Table 6). Mean value of the Wells score was significantly higher in haemodynamically unstable patients (6.8 to 4.8), P = 0.008). We made a correlation between the Quanadli index of obstruction in haemodynamically unstable and haemodynamically stable patients (Table 7). There was a higher mean value of the Quanadli index in the haemodynamically unstable group, but
The Clinical Respiratory Journal (2015) • ISSN 1752-6981 © 2015 John Wiley & Sons Ltd
Obradovic´ et al.
Correlation between Wells and Quanadli in PE
Table 5. Mean values of the Wells score in haemodynamically unstable and haemodynamically stable patients Wells score n Haemodynamically Unstable Haemodynamically Stable Total
Maximum
2.02
4.5
10.0
15 35
5.656
1.81
1.5
10.5
50
6.00
1.93
1.5
10.5
Discussion Diagnosing pulmonary embolism still poses a challenge to clinicians, in spite of all the available modern diagnostic procedures. Based on the autopsy findings, diagnosis of PE is missed in up to 30%–50% of patients (14). It is not possible to diagnose PE based only on symptoms and clinical signs, since the sole clinical evaluation is insufficient to confirm or exclude PE. In our study, we used the Wells scoring system and the modified Wells scoring system to determine clinical probability of PE. In PIOPED trial (3) prevalence of PE was 9% in patients classified as having low clinical probability of PE, and 30% in the group of patients with intermediate probability of PE, while prevalence Table 6. Mean values of the Wells score in haemodynamically unstable patients with pulmonary embolism (PE) and the patients in which PE was excluded Wells score
X 6.80
SD
Minimum
Maximum
15
2.02
4.5
10.0
10 25
4.80 6.00
0.95 1.93
3.0 3.0
6.0 10.0
N
Minimum
X 6.80
the difference did not bear statistical significance (31.33% to 26.64%, P = 0.062).
Hemodynamically unstable PE excluded Total
Standard Deviation
was 68% in the group with high clinical probability of PE. Our results are different, most probably because of the fact that overall prevalence in our patients was 83.33% (100% in patients classified as having low clinical probability of PE, 76.64% in the group of patients with intermediate probability of PE and 100% in the group with high probability of PE). Mohammad et al. (4) did a study which included 99 patients, and they also used the Wells scoring system to determine clinical probability of PE. There were eight patients (8.1%) in the group with low clinical probability of PE, 68 (68.7%) were classified as having intermediate clinical probability and 23.3% as having high clinical probability. In this study, PE was confirmed in 68% of patients whose Wells score was between 2–6 points, and in 90% of patients whose Wells score was >6 points. In our study, PE was confirmed in 33 out of 43 patients (prevalence of PE 76.74%) in the group with Wells score of 2–6 points, and PE was confirmed in all 16 patients with Wells score of >6 points (prevalence 100%). These findings confirm that the higher Wells score, the higher prevalence of PE (7, 15). Diversity of data cited in the above-mentioned studies can be explained by different prevalence of PE in general. Unfortunately, we have no valid data on PE prevalence in our country; therefore, the Wells scoring system was elected according to the results of Ceriani et al. meta-analysis (7) that recommended either Wells (10) or Miniati scoring system (16) for hospitalized patients.
Table 7. Mean values of the Quanadli index of obstruction in haemodynamically unstable and haemodynamically stable patients Quanadli index (%)
X 31.33
SD
Minimum
Maximum
15
16.34
2.5
50.0
35 50
26.64 28.05
15.12 15.47
5.0 2.5
55.0 55.0
n Haemodynamically unstable Haemodynamically stable Total
The Clinical Respiratory Journal (2015) • ISSN 1752-6981 © 2015 John Wiley & Sons Ltd
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Correlation between Wells and Quanadli in PE
One retrospective observational research (17) included 286 hospitalized patients with suspected PE (patients had previously received prophylactic doses of heparin), and PE was confirmed in 57 patients (20%). There was 95% sensitivity in this group, and 27% specificity, 27%, PPV 9% and NPV 99% for modified Wells criteria, which is in line with our results. However, our research has shown a high PPV, since the prevalence of PE was much higher in our group of patients (83.33%). One prospective trial included 613 patients (18) with suspected PE during their hospitalization, and the diagnosis was confirmed in 36% patients. Of these patients 394 (66%) were classified as having low clinical probability of PE, according to the modified Wells score, and 219 patients (34%) were classified as having high clinical probability of PE. The modified Wells criteria yielded sensitivity of 65%, specificity of 81%, PPV was 66% and NPV was 80%. Our results for NPV are different, since prevalence of PE in patients with low clinical probability was over 70%. The Quanadli index estimates the degree of pulmonary blood vessels obstruction in PE as visualised by CTPA (13). Quanadli index has proven simple to calculate, reproducible and adequate to quantify PE. In our study, there was no statistically significant correlation between the Wells score values and the degree of obstruction estimated by Quanadli index. Mean Wells score was the highest in the group of patients with Quanadli index higher than 50%, but we have not been able to show statistical significance of this correlation. According to Rodrigues et al. (19), there is a statistically significant correlation between higher values of the Wells score and higher values of the Quanadli index; however, this trial excluded patients with low clinical probability of PE. The study from Turkey (20) also showed statistically significant correlation between the values of Wells score and the degree of pulmonary vessels obstruction evaluated by CTPA (r = 0.470, P < 0.001). In our research, there was no statistically significant difference between mean values of the Wells score and the degree of obstruction estimated by the Quanadli index (ANOVA, F = 0.636, P = 0.533), and there was a weak correlation between the values of the Wells score and the Quanadli index, which was not statistically significant (r = 0.14; P = 0.289). According to our results, the Wells score does not predict the degree of pulmonary obstruction in patients with PE. On the other hand, our results show statistically significant higher value of the Wells score in patients with haemodynamically unstable PE compared to haemodynamically stable patients and
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Obradovic´ et al.
patients in whom PE was excluded. Also, mean Quanadli index was higher in the group of patients with haemodynamically unstable PE than in the group with haemodynamically stable PE, but there was no statistical significance. Mean value for the obstruction index in our haemodynamically unstable patients was 31.33%, while the colleagues from Turkey found this index to be 52.9% in haemodynamically unstable patients. A possible explanation is that in our study CTPA and Quanadli indexing followed thrombolytic therapy and haemodynamic stabilization. Another limitation of our study is that CTPA was performed on average of 4 days after the admission when the patients had already received either anticoagulants or thrombolytics. This suggests that the relationship between the degree of clinical probability of PE and the degree of pulmonary vascular obstruction is largely time dependent.
Conclusion In our study, modified Wells criteria had high sensitivity but low specificity in PE diagnostics. There was no significant correlation between the degree of clinical probability of PE and the degree of pulmonary vascular obstruction, which may be because of the delayed CTPA diagnostic in some patients.
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