Light exposure can oxidize bilirubin, producing structurally altered forms and affecting results. Which statement is true?

• A. Light exposure oxidizes bilirubin, leading to erroneous results
• B. Refrigeration stabilizes bilirubin
• C. Light exposure has no effect
• D. Sample handling does not matter

Answer: (A)

Bilirubin is photolabile, meaning it can undergo chemical changes when exposed to light. When light hits bilirubin, it can be photo-oxidized to different forms (photoisomers) that have distinct structures and absorbance properties. These altered forms don’t react the same way in common bilirubin assays, so the measured value can be inaccurate or unreliable. In practice, keeping samples shielded from light—such as using amber tubes or wrapping samples and analyzing promptly—is the key step to prevent artifactual results. Refrigeration helps slow some processes but does not address the primary problem of light-driven oxidation, which is why the statement highlighting light exposure as the cause of erroneous results is the correct one.