The role of procalcitonin (PCT) in parapneumonic pleural effusion (PPPE) as a diagnostic and prognostic biomarker of the outcome has not been examined before.
From the emergency department, 82 adult patients with pleural effusions were enrolled in this prospective study and divided into the following two groups: the PPPE group (n = 45); and the non-PPPE group (n = 37). Levels of pleural fluid (PF) PCT and serum (S) PCT were determined in all patients after study enrollment as well as on day 3 only in the PPPE group by a newly developed time-resolved, amplified, cryptate emission assay.
Both PF-PCT and S-PCT levels were significantly higher in the PPPE group than the non-PPPE group (p = 0.01 and 0.0003, respectively). S-PCT had a better diagnostic performance than PF-PCT, with an area under the curve of the receiver operating characteristic of 0.834 for S-PCT and 0.752 for PF-PCT (p = 0.006). In the PPPE group, both PF-PCT and S-PCT levels on days 1 and 3 were significantly higher in patients who were in high-severity risk classes (all p values < 0.05). Day 3 PF-PCT/S-PCT ratios were significantly lower in patients who needed chest tube drainage for > 7.5 days (corrected p = 0.02).
S-PCT has higher diagnostic accuracy than PF-PCT in differentiating PPPEs from non-PPPEs. However, both PF-PCT and S-PCT are useful in the severity assessment of patients with PPPEs. The PF-PCT/S-PCT ratio may help to predict prolonged chest tube drainage.