Question: Our lab performs two testosterone tests, one baseline, and one following the patient receiving a testosterone injection. Before each test, the lab takes three blood samples at 20-minute intervals and pools the specimen. Should we report this as two units of 84402 with modifier 91 for the repeat test? Michigan Subscriber Answer: No, you should not report two units of the blood test 84403 (Testosterone; total) using modifier 91 (Repeat clinical diagnostic laboratory test) in this scenario. What you describe is actually a single specific test for testosterone response. The panel test does include performing 84403 twice, but there’s more to it than that. The panel requires using a pooled blood sample for each test, because testosterone level can be quite variable in blood. The test also includes a testosterone dose, as you mentioned, so that the second blood test can identify the patient response. If the testosterone level does not increase, it can help the clinician diagnosis certain conditions. The correct code for the testosterone response panel is a single unit of 80414 (Chorionic gonadotropin stimulation panel; testosterone response. This panel must include the following: Testosterone (84403 x 2 on 3 pooled blood samples)).