Ascitic fluid to serum bilirubin concentration ratio for the classification of transudates or exudates

We compared the ascitic fluid to serum bilirubin ratio with three other ways of classifying ascitic fluid to the categories of exudate or transudate: the serum-ascites albumin gradient, the total protein concentration of the fluid, and the adaptation of Light's criteria for the detection of pleural fluid exudate, i.e., fluid to serum protein or LDH ratio or fluid LDH concentration. (Recently it has been reported that the pleural fluid to serum bilirubin ratio is statistically equivalent to Light's criteria.) Also, we evaluated whether the addition of the bilirubin ratio to the other criteria increases their diagnostic accuracy.

Eighty-one specimens of ascitic fluid from 81 different patients were obtained. They were analyzed prospectively by SMA12, whereas the category of the fluid was determined according to the clinical diagnosis. The diagnostic accuracy of each criterion alone and in combination with the bilirubin ratio, with reference to the contended etiology, were evaluated.

The best criterion is the albumin gradient (overall accuracy = 0.84). The bilirubin and LDH ratio criteria had equivalent overall accuracy (0.815 and 0.802, respectively). The addition of the bilirubin ratio to any criterion did not improve its predictive or overall accuracy.

Ascitic fluid to serum bilirubin ratio is an additional marker for the distinction of transudate from exudate. A ratio > 0.6 has a statistically significant association with exudate.