Pleural fluid serum bilirubin ratio for differentiating exudative and transudative effusions

INTRODUCTION: In pleural effusion, differentiating exudative and transudative fluid is an important clinical evaluation. The objective of the study was to determine the efficacy of pleural fluid serum bilirubin ratio in differentiating exudative and transudative effusions. In resource-limited settings with no facilities to measure lactate dehydrogenase levels, using pleural fluid bilirubin ratio may help in better clinical decision. METHODS: It was a cross sectional study, conducted in the emergency department of Tribhuvan University Teaching Hospital. All the patients attending for emergency care with pleural effusion from 6th Jan 2015 to 5th Jan 2016 were included. The cases were divided as exudates and transudates on basis of final diagnosis. Serum and pleural fluid specimen were collected and sent for investigations. The data for various laboratory parameters especially those of lights criteria and bilirubin ratio were then analyzed and fluid nature was compared with results from parameters and final diagnoses. RESULTS: Among 103 cases, 74 (71.84%) had exudate and 29 (28.16%) had transudate. The commonest cause of effusion was pneumonia 37 (35.92%), second being tubercular 24 (23.30%) followed by malignant effusion 13 (12.60%), congestive heart failure 12 (11.65%), chronic kidney disease 11 (10.67%) and liver cirrhosis 6 (5.82%). The mean bilirubin ratio for exudates exceeded that for transudates. Considering the cutoff point of 0.6, the sensitivity, specificity, positive predictive value and negative predictive value were respectively 88.00%, 93.00%, 97.00% & 75.00%. CONCLUSIONS: Pleural fluid serum bilirubin ratio can be utilized as a diagnostic tool for differentiating exudative and transudative effusions.