It’s an HIV test. Since we commonly pronounce HIV as individual letters, and the "H" sounds like "eich", we use the indefinite article "an".

It’s an HIV test. The rule for using "a" or "an" is based on pronunciation, not spelling. Since we commonly pronounce HIV as individual letters, and the "H" sounds like "eich", we use the indefinite article "an".

An HIV test should be used to diagnose the disease.

A HIV test should be used to diagnose the disease.

Follow the same strategy with other similar phrases and expressions, such as an HIV infection, an HIV patient, an HIV prevention program, an HIV diagnosis, etc.

An HIV infection is typically treated with antiretroviral medicines.

We launched an HIV prevention campaign that aims to educate people about the disease.

We also use the article "an" to say an H, an HDL (High-Density Lipoprotein), an HDMI (High-Definition Multimedia Interface), an HPV infection (Human Papilloma Virus), an HTML element, or an HTTP client.

Does your laptop have an HDMI input?