Lab Med Online.  2018 Oct;8(4):127-134. 10.3343/lmo.2018.8.4.127.

Clinical Usefulness of Direct/Total Bilirubin Ratio

  • 1Department of Laboratory Medicine, Hanyang University Guri Hospital, Guri, Korea.


The direct/total (d/t) bilirubin ratio can be used to distinguish the causes of jaundice in many patients who have increased levels of direct and indirect bilirubin. However, the reference range of the d/t ratio has not been established, hindering its clinical usefulness. This study assessed the clinical usefulness of the d/t ratio.
Paired total bilirubin and direct bilirubin tests (N=4,357) of cholestasis, hemolytic anemia, and neonatal jaundice were evaluated. Regression analyses were performed between total bilirubin and direct bilirubin, and between total bilirubin and the d/t ratio for each disease. Theoretical correlation models were established and used to compare the regression analyses data.
The theoretical model and regression equation between total bilirubin and direct bilirubin displayed linear correlations for all three cholestatic diseases. The model and regression equation between total bilirubin and the d/t ratio showed reciprocal curve correlations for the cholestatic diseases. When the total bilirubin concentration exceeded approximately 10 mg/dL, the rate of change of the d/t ratio decreased and converged to a constant value between 0.7 and 0.9.
If the total bilirubin concentration exceeds 10 mg/dL, cholestatic diseases can be diagnosed if the d/t ratio is more than 0.7. However, if the total bilirubin concentration is lower than 10 mg/dL, cholestatic diseases should be considered even if the d/t ratio is lower than 0.7. Therefore, use of the d/t ratio with total bilirubin could prove to be valuable in clinical settings.


Bilirubin; Hyperbilirubinemia; Cholestasis
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