PLEURAL FLUID CHEMICAL-ANALYSIS IN PARAPNEUMONIC EFFUSIONS - A METAANALYSIS

Controversy exists regarding the clinical utility of pleural fluid pH, lactate dehydrogenase (LDH), and glucose for identifying complicated parapneumonic effusions that require drainage. in this report, we perf ormed a meta-analysis of pertinent studies, using receiver operating c haracteristic (ROC) techniques, to assess the diagnostic accuracy of t hese tests, to determine appropriate decision thresholds, and to evalu ate the quality of the primary studies. Seven primary studies reportin g values for pleural fluid pH (n = 251), LDH (0 = 114), or glucose (n = 135) in pneumonia patients were identified. We found that pleural fl uid pH had the highest diagnostic accuracy for all patients with parap neumonic effusions as measured by the area under the ROC curve (AUG = 0.92) compared with pleural fluid glucose (AUG = 0.84) or LDH (AUG = 0 .82). After excluding patients with purulent effusions, pH (AUG = 0.89 ) retained the highest diagnostic accuracy. pleural fluid pH decision thresholds varied between 721 and 7.29 depending on cost-prevalence co nsiderations. The quality of the primary stud ies was the major limita tion in determining the value of plural fluid chemical analysis. We co nclude that meta-analysis of the available data refines the applicatio n of pleural fluid chemical analysis but a clearer understanding of th e usefulness of these tests awaits more rigorous primary investigation s.