Diagnosis of chylous abdominal effusions: what is the triglyceride threshold value?

Abstract

Introduction: Chylous abdominal effusions are serious complications that can be triggered by various aetiologies. The biochemical diagnosis of chyle leakage in ascites or in peritoneal fluid capsules relies on the detection of chylomicrons. Assaying the fluid's concentration of triglycerides is still the first-line tool. Given that only one comparative study has sought to quantify the value of the triglyceride assay for diagnosing chylous ascites in humans, our objective was to provide practical triglyceride thresholds.

Materials and methods: We conducted a 9-year, retrospective, single-centre study of adult patients and compared a triglyceride assay with lipoprotein gel electrophoresis for the analysis of 90 non-recurring abdominal effusions (ascites and abdominal collections) of which 65 were chylous.

Results: A triglyceride threshold of 0.4 mmol/L was associated with a sensitivity > 95%, and a threshold of 2.4 mmol/L was associated with a specificity > 95%. According to Youden index, the best threshold was 0.65 mmol/L with a sensitivity of 88 (77-95)%, a specificity of 72 (51-88)%, and, in our series, a positive predictive value of 89 (79-95)% and a negative predictive value of 69 (48-86)%.

Conclusions: In our series, cut-off of 0.4 mmol/L could be used for ruling-out diagnosis of chylous effusions, while cut-off of 2.4 mmol/L could be used for reasonably confirming diagnosis.

Keywords: chylous ascites; lipoprotein gel electrophoresis; triglycerides.

Figure 1

The ROC curve for prediction of the presence of chyle in ascites liquid, based on the triglyceride concentration.

Figure 2

Comparison of the triglyceride distribution in chylous samples (in grey) vs. non-chylous samples (in black). Black vertical lines show the optimal threshold according to Youden’s index (the continuous line) and its 95% confidence interval (the dashed line). The vertical dotted lines show the thresholds reported by Staat et al. (1.2 mmol/L) and Thalers et al. (2.1 mmol/L).