Final answer:
While the specific frequency of HIV testing for active duty service members is not given, the standard in the U.S. is annual testing, especially for those at higher risk. Hospitals may conduct widespread HIV testing if exposure risks are identified, using tests such as the antibody-antigen test and NAT.
Step-by-step explanation:
The frequency at which active duty service members are tested for HIV is not explicitly stated in the provided reference material. However, the standard practice in the United States for adults, including those in the military, is to have HIV screening at least annually, especially if the individual is at higher risk for HIV infection.
The decision to test every patient in a hospital setting, as mentioned in the scenario you provided, might be due to a potential exposure risk identified within that healthcare environment, prompting the need for widespread testing to ensure early detection and treatment of potentially infected individuals.
Several types of tests can be used to determine if a patient has HIV, including the fourth-generation antibody-antigen test, the nucleic acid test (NAT), and indirect ELISA, which each have different windows of detection post-exposure and can sometimes lead to false positives or negatives if performed too early after potential infection.