The use of pleural fluid procalcitonin and C-reactive protein in the diagnosis of parapneumonic pleural effusions: a systemic review and meta-analysis

Background: We aimed to perform a systematic review and meta-analysis of the diagnostic performance of pleural fluid procalcitonin (PCT) or C-reactive protein (CRP) in differentiating parapneumonic effusion in patients with pleural effusion.

Methods: We searched the EMBASE, MEDLINE, and Cochrane database in December 2011. Original studies that reported the diagnostic performance of PCT alone or compared with that of other biomarkers for differentiating the characteristics of pleural effusion were included.

Results: We found 6 qualifying studies including 780 patients with suspected parapneumonic effusion and 306 confirmed cases of parapneumonic effusion. Six studies examined the diagnostic performance of pleural fluid PCT, 3 also tested for serum PCT, and another 3 tested for serum CRP. The bivariate pooled sensitivity and specificity were as follows 0.67 (95% confidence interval [CI], 0.54-0.78) and 0.70 (95% CI, 0.63-0.76), respectively, for pleural fluid PCT; 0.65 (95% CI, 0.55-0.74) and 0.68 (95% CI, 0.62-0.74), respectively, for serum PCT; and 0.54 (95% CI, 0.47-0.61) and 0.77 (95% CI, 0.72-0.81), respectively, for serum CRP. There was evidence of significant heterogeneity (I(2)=55.0%) for pleural fluid or serum PCT but not for CRP (I(2)=0.0%).

Conclusion: The existing literature suggests that both pleural fluid and serum PCT tests have low sensitivity and specificity for differentiating parapneumonic effusion from other etiologies of pleural effusion. Compared with PCT, serum CRP has higher specificity and a higher positive likelihood ratio, and thus, it has a higher rule-in value than PCT.