Which laboratory test should be performed no more than 7 days before prescribing pre-exposure prophylaxis with emtricitabine/tenofovir disoproxil (Truvada)?

The appropriate laboratory test to perform no more than 7 days before prescribing pre-exposure prophylaxis (PrEP) with emtricitabine/tenofovir disoproxil (Truvada) is antibody testing for HIV. This test is crucial because the primary concern before initiating PrEP is to confirm that the individual is HIV-negative. If a person is already HIV-positive and they begin PrEP, it can lead to drug resistance and treatment failure. Therefore, testing for HIV antibodies ensures that those starting PrEP are at the right point in their HIV status, aligning perfectly with the guidelines for safe PrEP usage.

Other laboratory tests may be relevant for assessing the overall health and risk factors of the patient but are not as time-sensitive in relation to the initiation of PrEP. For example, while CD4 count testing can provide insight into an individual's immune status, it is not typically required prior to starting PrEP. Hepatitis B panel is also important due to the risk of co-infection, but it doesn't need to be performed within the same tight timeframe as the HIV test when initiating PrEP. A complete blood count (CBC) assesses general health but does not provide specific information regarding HIV status. Therefore, the focus on recent HIV