Liver
Total bilirubin
Total bilirubin measures the combined conjugated (direct) and unconjugated (indirect) bilirubin in blood, the yellow-orange pigments formed as haemoglobin from ageing red cells is broken down and processed by the liver. As a point-of-care liver marker it gives a rapid, near-patient indication of how effectively bilirubin is being produced, conjugated and cleared.
Why it is measured
Total bilirubin is used to investigate jaundice and to assess liver and biliary function, helping separate raised red-cell breakdown from hepatic and post-hepatic (obstructive) processes when read alongside other liver tests. In newborns it is central to detecting and monitoring hyperbilirubinaemia at the bedside against age-specific treatment thresholds.
| Typical range | Indicative adult range approximately 3 to 21 micromol/L (about 0.2 to 1.2 mg/dL). Ranges vary by method, analyser and laboratory, and neonatal results are interpreted against age-specific (hour-of-life) treatment charts rather than the adult range. |
|---|---|
| Sample | Capillary or venous whole blood, or serum/plasma (commonly lithium heparin) depending on the analyser. Sample volumes are small, on the order of tens of microlitres up to about 100 microlitres depending on the device. Bilirubin is light-sensitive and affected by haemolysis, so samples should be protected from light and analysed promptly. |
| Turnaround | Typically about 2 to 12 minutes on benchtop POCT chemistry analysers, and under about 1 minute on whole-blood co-oximetry blood gas systems. |
Point of care devices that report it
- Abbott (Abaxis) Piccolo Xpress: benchtop chemistry analyser, enzymatic bilirubin oxidase method on liver and metabolic reagent discs
- Samsung LABGEO PT10: cartridge-based chemistry analyser, total bilirubin within its hepatic/liver panel from whole blood, serum or plasma
- Roche Reflotron Plus: dry-chemistry reflectance-photometry system with a bilirubin test strip among its parameters
- Radiometer ABL90 FLEX PLUS: whole-blood neonatal bilirubin via the co-oximetry module on a blood gas analyser
Questions, answered
Does a point-of-care total bilirubin result replace a laboratory test?
Point-of-care testing is designed for rapid triage, screening and bedside monitoring, giving results in minutes near the patient. Some POCT analysers show a small method bias for bilirubin compared with central-laboratory methods, so local correlation, quality control and, where appropriate, confirmatory laboratory testing remain important. This is general operational guidance, not a substitute for clinical judgement.
Why might a point-of-care and a laboratory bilirubin result differ?
Different platforms use different chemistries (for example bilirubin oxidase, diazo, dry-chemistry reflectance or co-oximetry), different sample types and separate calibration, so method-specific reference ranges apply. Pre-analytical factors such as haemolysis and exposure to light can also lower or alter measured bilirubin. Results are best compared within the same method over time rather than across platforms.
Can these analysers separate direct and indirect bilirubin?
Total bilirubin is the combined conjugated and unconjugated value. Some chemistry analysers can additionally report direct (conjugated) bilirubin and derive the indirect fraction by calculation, while co-oximetry neonatal bilirubin on blood gas analysers reports a total value only. The exact menu is device and configuration dependent, so check the analyser's reportable parameters.