Establishment of triglyceride cut-off values to detect chylous ascites and pleural effusions

Lipoprotein electrophoresis is the gold standard for the detection of chylous ascites and pleural effusions. It is, however, not suitable as a front-line test and not widely available. Most clinicians must rely solely on the quantitative determination of lipids. The aim of this work was to establish lipid cut-off values for the presence of chylomicrons in pleural and peritoneal fluid.

Triglyceride and cholesterol levels from 113 peritoneal and 154 pleural fluid samples investigated for chylomicrons via lipoprotein electrophoresis were considered. Receiver operating characteristic analyses were performed and cut-off levels determined.

54 peritoneal and 59 pleural fluid samples were positive for chylomicrons. In peritoneal fluid, triglycerides and triglycerides/cholesterol ratio exhibited areas under the curve (AUC) not significantly different from each other, but significantly larger than cholesterol alone. The AUC for triglycerides in pleural fluid was significantly larger than the AUCs for cholesterol and the triglycerides/cholesterol ratio. Triglyceride cut-offs with maximum Youden-Index, sensitivity >95%, and specificity >95% were calculated to be 187, 148, and 246mg/dl (2.13, 1.69, and 2.80mmol/l) for peritoneal fluid, and 240, 94, and 240mg/dl (2.74, 1.07, and 2.74mmol/l) for pleural fluid.

Triglyceride levels are the best parameter to detect chylous body fluids when lipoprotein electrophoresis is not available. Single-point triglyceride cut-offs of 187 and 240mg/dl (2.13 and 2.74mmol/l) or alternatively equivocal ranges of 148-246 and 94-240mg/dl (1.69-2.80 and 1.07-2.74mmol/l) were established for peritoneal and pleural fluid, respectively.