Which of the following methods is not used for quantification of serum bilirubin?

• A. Bilirubinometer
• B. Jendrassik and Grof
• C. Zimmerman
• D. Bilirubin oxidase

Answer: (C)

Quantifying serum bilirubin relies on colorimetric or enzymatic methods that produce a stable color proportional to the bilirubin concentration. The Jendrassik-Grof method is a well-established colorimetric (diazo-based) technique that allows accurate measurement of total and direct bilirubin in serum. A bilirubinometer refers to an instrument used to obtain bilirubin measurements photometrically, either in serum or transcutaneously, and is a practical tool for quantification. Bilirubin oxidase provides an enzymatic route where bilirubin is converted to a colored product or to biliverdin, yielding a direct readout of bilirubin concentration on automated systems.

The Zimmermann approach, however, is not used for quantifying serum bilirubin in routine clinical practice. It is an older method with limitations in precision, specificity, and compatibility with modern analyzers, so it has largely been replaced by the more reliable Jendrassik-Grof and enzymatic methods.