Which test requires a patient to be in the supine position?

The EKG, or electrocardiogram, is the test that requires a patient to be in the supine position. This position allows for better electrode placement on the chest, which is essential for obtaining accurate heart rhythm readings and electrical activity measurements. Being supine also helps ensure the comfort of the patient while minimizing movement that could interfere with the test results.

Other tests listed do not specifically necessitate the supine position. A complete blood count is typically performed via blood draw while the patient can be sitting or standing. A urinalysis requires the patient to provide a urine sample, which is not dependent on body position. Similarly, a lipid panel, like the complete blood count, involves drawing blood that can be done with the patient either sitting or in another comfortable position. Hence, the requirement of the supine position is unique to the EKG among the choices presented.