C-reactive protein and serum amyloid A levels in discriminating malignant from non-malignant pleural effusion

Introduction Distinction between malignant and non-malignant pleural effusion is of great importance in the patient management. The aim We examined the diagnostic value of C-reactive protein (CRP) and serum amyloid A (SAA) in distinguishing different etiologies of pleural effusion and if they could discriminate between malignant and non-malignant pleural effusions. Subject and methods CRP and SAA levels in both serum and pleural fluid were measured in 92 patients with pleural effusion. Of the 92 patients included in our study; 44 were diagnosed with malignant pleural effusions (group I) [with male to female ratio (M/F) 23/21 and mean age 57.7 ± 11.5 years in the form of mean ± 2SD] and 48 were diagnosed with non-malignant pleural effusion (group II) [with M/F ratio 33/15 and mean age 54.7 ± 10.4 years in the form of mean ± 2SD]. Results CRP and SAA values were significantly higher in both serum and pleural effusion of malignant vs. non-malignant group ( P < 0.003), but there was no statistical significant difference as regards pleural/serum CRP and pleural/serum SAA ratios between the two groups ( P = 0.148 and P = 0.453 respectively). A statistically significant positive correlation between pleural fluid CRP and pleural fluid SAA in malignant and non-malignant effusions was detected ( r = 0.315 and P = 0.002 respectively). Diagnostic performance of pleural fluid CRP and pleural fluid SAA in both infectious and malignant pleural effusions showed that at a cutoff value of 96.15 μg/ml for CRP; diagnostic sensitivity was 61% and specificity was 45%, while for pleural fluid SAA, a cutoff value of 137.5 μg/ml was associated with 41% sensitivity and 93% specificity. Conclusion Measurement of SAA and CRP levels in pleural fluid has good diagnostic utility in differentiation between malignant and non-malignant pleural effusion and pleural SAA has a better diagnostic performance than CRP.