Which of the following tests is mandatory for the medical examination?

Urinalysis is a mandatory component of the medical examination for commercial driver's license (CDL) holders as mandated by the Federal Motor Carrier Safety Administration (FMCSA). This test is primarily conducted to check for a variety of health conditions, including diabetes, kidney disease, and the presence of substances that may affect a driver's ability to operate a vehicle safely.

The results of the urinalysis provide valuable insights into the driver's overall health and can detect medical issues that could lead to disqualifying conditions. It is also part of ensuring that drivers do not have any substances in their system that could impair their ability to drive. While other tests like audiometry and sleep studies may be important in certain circumstances, they are not universally required as part of the standard examination for all drivers. An electrocardiogram is generally not mandatory unless there are specific concerns regarding the individual's heart health.