The most widely used methods for bilirubin measurement are those based on the:

• A. Jaffe reaction
• B. Schales and Schales method
• C. 8-Hydroxyquinoline reaction
• D. Jendrassik-Grof method

Answer: (D)

Bilirubin is most reliably measured using a diazo-based colorimetric approach, where bilirubin reacts with a diazonium salt to form a colored azobilirubin that can be read spectrophotometrically. The Jendrassik-Grof method is the go-to version of this approach because it uses an accelerator and solubilizing agents that speed up and complete the reaction for both conjugated and unconjugated bilirubin, yielding a stable endpoint. This makes the assay highly accurate, repeatable, and readily automatable across a wide range of sample types, which is why it has become the standard method in most clinical laboratories. Other older methods either rely on less complete reactions, require solvent extraction, or are less compatible with routine automation, making them less favored in contemporary practice.