Procalcitonin as a diagnostic marker in differentiating parapneumonic effusion from tuberculous pleurisy or malignant effusion

Objectives

Differential diagnosis of exudative pleural effusions can be difficult, despite the use of several biomarkers. Serum procalcitonin (s-PCT) is a well-known biomarker for systemic bacterial infections. However, the usefulness of pleural fluid procalcitonin (pf-PCT) in clinical practice has not been established. This study evaluated the usefulness of PCT measurements in differentiating parapneumonic effusion (PPE) from tuberculous (TB) pleurisy or malignant effusion.

Design and methods

Ninety eight adult patients diagnosed with exudative pleural effusion were enrolled and allocated into the PPE group (n = 32), TB pleurisy group (n = 40), or malignant effusion group (n = 26). Both s-PCT and pf-PCT concentrations were measured at admission using an immunoluminometric assay.

Results

Both s-PCT and pf-PCT were significantly increased in the PPE group compared with the TB pleurisy or malignant effusion groups (p < 0.001). The optimal cut-off value for s-PCT in the diagnosis of PPE was 0.18 ng/mL (sensitivity 83.3%, specificity 81.0%). The pf-PCT cut-off value was 0.16 ng/mL (sensitivity 81.5%, specificity 72.1%). Serum PCT exhibited better diagnostic accuracy than pf-PCT, with areas under the receiver operating characteristic curves of 0.842 for s-PCT and 0.784 for pf-PCT (p = 0.015). In addition, s-PCT and pf-PCT showed better diagnostic accuracy than serum C-reactive protein (p = 0.005 and p = 0.023, respectively).

Conclusions

Measurement of s-PCT and pf-PCT is useful in differentiating PPE from TB pleurisy and malignant effusion. Both s-PCT and pf-PCT may be useful biomarkers in the differential diagnosis of exudative pleural effusions.