Pleural effusion: criteria for distinction between transudates and exudates

ABSTRACT

This study aimed to assess the diagnostic value of the new biochemical criteria proposed to discriminate pleural transudates from exudates and to compare their efficiency with those of Light's criteria as well as to study the effect of diuretics on different biochemical parameters among cases with transudative pleural effusion. A total of 110 patients with pleural effusion was included in the study. All patients were subjected to history taking, clinical examination, chest X-ray and ultrasound and Doppler echocardiography. Pleural fluid and blood samples were examined for the measurement of total proteins, albumin, lactate dehydrogenase [LDH], cholesterol, cholinesterase, bilirubin and serum pleural fluid albumin gradient [SPAG]. Forty patients had transudative effusion, while 70 had exudative effusion. Among patients with transudates, the biochemical criteria were reevaluated after diuretic therapy. SPAG was the most specific biochemical parameter in identifying exudates, while pleural/serum cholinesterase ratio was the most sensitive one. Moreover, both parameters were more accurate than Light's criteria in the differentiation between transudates and exudates. Diuretics had a significant effect on Light's criteria with a conversion of transudates into pseudo-exudates in many cases; in contrast, diuretics had no significant effect on SPAG, cholinesterase ratio, bilirubin ratio, pleural cholesterol and pleural/serum cholesterol ratio