TỰ XÉT NGHIỆM HIV CÓ CHÍNH XÁC KHÔNG?​

Key points

• Most devices for self-testing (home testing) are modified versions of professional tests, with comparable sensitivity and specificity.
• Self-tests are usually reliable for long-standing infections, but are sometimes unable to detect recent HIV infections acquired in the past few weeks.
• Like any screening test, a reactive (‘positive’) result must be confirmed with one or two follow-up tests.
• Studies show that most people can accurately and reliably use self-testing devices.

HIV self-testing involves collecting your own specimen (oral fluid or blood) and using a rapid HIV test kit. You perform the whole test yourself, including reading and interpreting the test result.

This is different from HIV self-sampling. With self-sampling, you collect your own sample and send it to a laboratory for analysis.

Self-testing is sometimes called ‘home testing’, because people often do it at home. The World Health Organization (WHO) recommends that HIV self-testing should be offered alongside existing HIV testing services.

Different types of tests

Self-tests are usually modified versions of rapid, point-of-care test kits that were originally designed for healthcare professionals. Their processes, packaging and instructions have been simplified so as to guide you through the steps of taking a test.

With some tests, you use a lancet to release a small quantity of blood from a fingerprick. Other tests require a sample of oral fluid, obtained by swabbing an absorbent pad around the outer gums, adjacent to the teeth.

Self-tests may be second- or third-generation HIV tests. They are only able to detect HIV antibodies, whereas the fourth-generation HIV tests which are normally used by healthcare professionals are also able to detect p24 antigen (a protein contained in HIV’s viral core that can be detected in the first few weeks after infection). Fourth-generation tests (Abbott CheckNOW) are therefore better at picking up recent infections.

Situations in which self-tests may not be accurate

Performance of self-tests is poorer in a number of situations. Results may not be accurate.

• In cases of recent HIV infection, during the test’s window period.
• In people with diagnosed HIV who are taking HIV treatment. These tests are not a reliable way to confirm that you still have HIV infection.
• In people who are taking pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP). If they acquire HIV, they may have a delayed antibody response, extending the window period.

• When test instructions have not been correctly followed – for example not enough blood has been collected.

What do the test results mean?

There are three possible test results:

1) Negative (may also be described as ‘non-reactive’). The test did not find any evidence of HIV infection. You probably don’t have HIV (so long as you aren’t testing in one of the situations described in the last section).

2) Reactive (often incorrectly described as ‘positive’ by manufacturers). The test assay has reacted to a substance in your blood. This does not necessarily mean that you are HIV positive. It means you need to take more tests to confirm the result. These extra tests are best done at a healthcare facility where they have access to the most accurate HIV testing technologies.

3) ‘Indeterminate’, ‘equivocal’ or ‘invalid’. The test result is unclear. Another test needs to be done.

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