What was the earliest method used for bilirubin determination?

• A. Ehrlich reaction using diazotized sulfanilic acid
• B. Jendrassik Groff method
• C. Van den Bergh reaction
• D. Direct spectrophotometry

Answer: (A)

The earliest approach to quantify bilirubin relied on a chemical color reaction where bilirubin couples with a diazonium salt to form a colored azo dye. This is achieved with diazotized sulfanilic acid in the Ehrlich reaction, producing azobilirubin whose color intensity can be measured. Because this colorimetric coupling was the first practical way to turn bilirubin content into a detectable signal, it represents the initial method used for bilirubin determination.

Later techniques built on this idea or refined the process, such as methods that separate conjugated and unconjugated bilirubin or that measure bilirubin directly without a diazo reaction.