Final answer:
The most appropriate next step would be to proceed with HIV screening after the patient has given his informed consent.
Step-by-step explanation:
The most appropriate next step would be to proceed with HIV screening after the patient has given his informed consent. In this case, the patient is a 17-year-old boy who confided in you about taking medication for tuberculosis. Although patients with tuberculosis may also have concomitant HIV infection, it is important to respect the patient's autonomy and privacy by offering HIV screening with his informed consent. It is not necessary to involve the patient's parents or wait until he finishes anti-tuberculosis therapy to perform the screening.