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

Clinical Usefulness of Direct/Total Bilirubin Ratio

• Hur K
• Park IK

• KMID: 2421002
• DOI: http://doi.org/10.3343/lmo.2018.8.4.127

Abstract

BACKGROUND
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.
METHODS
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.
RESULTS
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.
CONCLUSIONS
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.

Keyword

Bilirubin; Hyperbilirubinemia; Cholestasis

MeSH Terms

Anemia, Hemolytic
Bilirubin*
Cholestasis
Humans
Hyperbilirubinemia
Infant, Newborn
Jaundice
Jaundice, Neonatal
Models, Theoretical
Reference Values
Bilirubin

Figure

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  Fig. 1. Correlations between total bilirubin and direct bilirubin concentrations (A) and between total bilirubin concentration and d/t ratio (B) in patients with cholestasis.

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  Fig. 2. Theoretical correlations between total bilirubin and direct bilirubin concentrations (A) and between total bilirubin concentration and d/t ratio (B) in cholestasis.

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  Fig. 3. Correlations between total bilirubin and direct bilirubin concentrations in patients with hemolytic anemia (A) and neonatal jaundice (B), and between total bilirubin concentration and d/t ratio in patients with hemolytic anemia (C) and neonatal jaundice (D).

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  Fig. 4. Theoretical correlations between total bilirubin and direct bilirubin concentrations (A) and between total bilirubin concentration and d/t ratio (B) in hemolytic anemia and neonatal jaundice.

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