[Influence of thoracentesis and pleural biopsy on biochemical parameters and cytology of pleural fluid]

To assess the influence of thoracentesis and pleural biopsy on biochemical parameters and cytology of pleural fluid from patients with lymphocytic exudate.

A prospective, descriptive study was performed in 72 patients with pleural effusion who had lymphocytic exudate and in whom biopsy was indicated. Biochemical variables and cytology of pleural fluid were analyzed at baseline, 48 hours later (immediately prior to biopsy), and 48 hours after biopsy.

The patients had a mean (SD) age of 63 (17) years, 57% were smokers, and 61% were men. Effusion was right-sided in 36% of patients, unilateral in 80%, and massive in 21%. The etiology was benign in 43 cases and neoplastic in 29 (40%). Pleural lactate dehydrogenase (LDH) was found to be increased following biopsy. This effect was significant in the overall population of 72 patients (649 [481] U/L just prior to biopsy and 736 [536] U/L 48 hours after biopsy; mean increase, 86 U/L; 95% confidence interval, 45-128 U/L; P< .001), in patients with pleural tumors (799 [529] U/L prior to biopsy and 957 [571] U/L 48 hours later, P< .001), and in those with LDH concentration greater than 266 U/L.

The results of our study show that a single thoracentesis procedure does not alter biochemical parameters or pleural cytology after 48 hours in lymphocytic exudates. Pleural needle biopsy leads to a significant increase in the concentration of LDH in patients with pleural tumors or higher baseline concentrations of LDH. Thoracentesis, pleural biopsy, or a combination of the two do not lead to significant changes in the number of eosinophils in pleural fluid.