AIDS blood tests: what they can tell you

A reactive screening result needs confirmation through the testing pathway used by the clinic. A clinician interprets the result alongside the type of test, the timing of possible exposure, symptoms, medicines and previous results.

An HIV screening test looks for signs of HIV infection, such as antibodies, an antigen, or viral genetic material, depending on the test. A CD4 count measures immune cells that HIV can affect, while a viral load measures HIV in the blood. These monitoring tests help assess immune health and response to treatment; neither should be interpreted alone as a new HIV diagnosis.

Testing too soon after a possible exposure can miss an infection because each test has a window period. The clinic can identify which test was used and whether repeat testing is appropriate.

Tell the clinician when the possible exposure happened and whether you have taken HIV prevention or treatment medicines. Do not delay urgent advice after a recent exposure while waiting to arrange a routine test. Keep the follow-up appointment so that a reactive screen can be confirmed and a negative result can be checked against the relevant window period.

If HIV is confirmed, prompt specialist care can arrange treatment and baseline checks. Do not stop prescribed HIV medicine or change the dose because of a single laboratory value.

Seek urgent medical assessment for difficulty breathing, confusion, fainting, severe weakness, inability to keep fluids down, or a rapidly worsening illness. These warning signs need assessment regardless of an HIV test result.

Contact a healthcare service promptly after a recent possible exposure, after a reactive result, or if fever, persistent diarrhoea, unexplained weight loss or recurrent infections develop. The next step depends on the clinical picture and testing timeline.

Ask which HIV test was performed, whether its window period affects your result, whether confirmation or repeat testing is needed, and when results will be available. If HIV is already diagnosed, ask what the CD4 count and viral load mean together and which medicines or illnesses could affect the readings.