Comparative Study of Pleural Fluid-to-serum Bilirubin Ratio and Light’s Criteria in Differentiating Exudative from Transudative Pleural Effusion

Abstract Introduction: Pleural effusion is a common diagnostic problem associated with significant morbidity. Its management mainly depends on the correct diagnosis of underlying disease. The present study is being done to evaluate the efficacy of pleural fluid-to-serum bilirubin ratio versus Light’s criteria in differentiating exudates from transudates. Materials and Methods: The present observational study was conducted in 60 patients with pleural effusion in the Department of Respiratory Medicine, Gandhi Medical College and Hospital, Secunderabad, TG, after obtaining clearance from the Institutional Ethics Committee over a period of 18 months. On the basis of underlying disease, the pleural effusions are grouped into transudate and exudate. Pleural fluid and serum samples of the study groups were collected and analyzed for bilirubin ratio, protein, lactate dehydrogenase, and Light’s criteria, and the results were compared. Results: In our study, out of total 60 patients with pleural effusion, 33 were exudates (55%) and 27 were transudates (45%). In the present study, it was observed that the sensitivity of Light’s criteria appears to be similar to pleural fluid/serum bilirubin ratio (96.97%) for classifying exudates, whereas in terms of specificity, the pleural fluid/serum bilirubin ratio (96.30%) was superior when compared to Light’s criteria (92.59%). The number of false-positive cases was minimum with pleural fluid/serum bilirubin ratio (positive predictive value [PPV] – 96.3%) when compared to Light’s criteria (PPV – 94.12%), whereas the negative predictive value for both Light’s criteria and bilirubin ratio was similar (96.1% and 96.3%). Conclusions: In the evaluation of pleural effusions in low-resource settings, to differentiate transudative and exudative pleural effusions, the pleural fluid-to-serum bilirubin ratio can be used as an easy and cost-effective alternative diagnostic tool.