Closed pleural needle biopsy: Predicting diagnostic yield by examining pleural fluid parameters

Objective: Pleural fluid parameters that predict a diagnostic closed pleural needle biopsy were investigated. Design: A retrospective analysis. Setting: The Institute of Pulmonology Hadassah University Hospital. Patients and methods: Forty-four patients who underwent closed pleural needle biopsies were included in this study Pleural fluid values of protein, glucose, lactate dehydrogenase (LDH), pH, and white blood cell count with differential cell counts, from patients with diagnostic and non-diagnostic pleural biopsies were compared. Results: Thirteen patients (29%) had diagnostic biopsies. Malignancy was identified in 10 patients (23%), of whom 70% had adenocarcinoma. Three other patients had non-malignant specific diagnosis. LDH levels in pleural fluid from patients with diagnostic pleural biopsy were higher than in patients with non-diagnostic pleural biopsies (1436 ± 333 U1^-1 vs. 775 ± 109 U1^-1; P<0.05). LDH levels less than 510 U1^-1 were highly predictive of a negative biopsy (negative predictive value of 86.6%). Follow up revealed malignancy including mesothelioma and lymphoma, in 10 of 30 (33%) patients with non-diagnostic biopsies, and one patient died of unrelated cause, while the pleural effusion either resolved, remained stable or an alternative benign process was identified in 19 patients (63%). Conclusions: Low levels of LDH (<510 U1^-1) were highly predictive of a negative pleural needle biopsy.Thus, LDH may serve as a useful guide in deciding whether to perform closed pleural biopsy or to proceed to thoracoscopically guided biopsy.