Biomarker: Bilirubin, Total

Overview

Total bilirubin measures the combined concentration of unconjugated and conjugated bilirubin in blood. Bilirubin is produced primarily from the breakdown of hemoglobin and is processed and excreted by the liver in bile. High levels may indicate increased red blood cell breakdown, impaired hepatic processing, liver disease, or bile duct obstruction, while low levels are usually not clinically significant. The test is clinically useful for evaluating jaundice, assessing liver and biliary disease, detecting hemolysis, and monitoring neonatal hyperbilirubinemia.

Clinical Use Cases

Evaluation of jaundice and yellowing of the skin or eyes.
Assessment of suspected liver disease, including hepatitis and cirrhosis.
Evaluation of possible bile duct obstruction or cholestasis.
Detection and characterization of hemolysis, particularly when interpreted with direct and indirect bilirubin.
Screening and monitoring for neonatal hyperbilirubinemia and jaundice.
Assessment of liver function and disease severity in clinical scoring systems such as the Model for End-Stage Liver Disease.
Monitoring changes during treatment or progression of hepatobiliary disease.

Specimen Types

Venous serum.
Venous plasma, including lithium-heparin or EDTA plasma when validated by the laboratory.
Urine may be used to assess bilirubin, particularly conjugated bilirubin, but is not the usual specimen for total serum bilirubin measurement.

Measurement Methods

Diazo-based colorimetric methods, including the Jendrassik-Grof method, commonly used for total bilirubin measurement.
Automated spectrophotometric assays that measure the absorbance of the colored azobilirubin product.
Direct spectrophotometry, particularly for neonatal or small-volume samples.
Enzymatic, oxidative, or chemical methods used on selected laboratory platforms.
High-performance liquid chromatography, mainly for specialized or research applications.

Test Preparation and Influencing Factors

Fasting is not universally required, but the healthcare provider or laboratory may request several hours of fasting, particularly when bilirubin is ordered as part of a broader panel.
Report all prescription medicines, over-the-counter medicines, and supplements because some medications can affect bilirubin concentrations or test results.
Do not stop any medication unless specifically instructed by a healthcare professional.
Collection timing is important in newborns because bilirubin concentrations change substantially during the first days of life; interpretation should account for the infant’s age in hours.
Prolonged fasting, strenuous exercise, some foods, and certain illnesses may influence bilirubin concentrations.
Protect serum or plasma from light because bilirubin is photosensitive and can degrade after collection.
Hemolysis during collection may interfere with measurement or complicate interpretation.
Reference intervals vary by laboratory, age, and clinical context; total bilirubin should be interpreted with direct and indirect fractions and other liver tests when levels are abnormal.