Pleural fluid biochemical analyses: a state-of-the-art review

Pleural fluid biochemical analyses are of great value in verifying the etiology of undiagnosed pleural effusions. The preanalytical phase of pleural fluid biochemical analyses refers to the potential errors associated with specimen collection procedures, transportation, and sample stability. The analytical phase refers to the matrix effects and interference. The post-analytical phase refers to the clinical interpretation of the biochemical analyses. This review summarizes the preanalytical, analytical, and postanalytical phases of pleural fluid biochemical analyses. Evidence regarding potential preanalytical errors (e.g. stability, interference, and effects of anticoagulants on biomarker results) was summarized. In addition, we compiled evidence on the clinical interpretation of pleural fluid biomarkers, particularly from systematic reviews and meta-analyses. Finally, we discuss the future directions of biochemical analyses of pleural fluid.