Why must urine specimens containing bilirubin be protected from light?

Protecting urine specimens containing bilirubin from light is crucial because bilirubin is photosensitive. When exposed to light, bilirubin can undergo photodegradation, leading to a breakdown of the compound and resultant loss of the analyte's integrity in the specimen. This degradation changes the concentration of bilirubin, which can lead to inaccurate test results and misinterpretation of a patient’s health condition.

In the context of the other choices, while preventing bacterial growth, maintaining specimen temperature, and avoiding contamination are important aspects of specimen handling, they do not directly relate to the stability of bilirubin. Ensuring that the specimen is shielded from light specifically preserves the critical biochemical component that may be evaluated during testing.