HIV factsheet: Types of HIV screening tests

The choice of HIV test may vary depending on clinical evaluation and patient history, including timing to potential exposure.

Screening tests
Third-generation enzyme immunoassay (EIA) test Fourth-generation test Point-of-care tests (POC)
The HIV enzyme immunoassay (EIA) test is used to detect antibodies produced in response to HIV infection. Results are reported as reactiveFootnote * or non-reactive. It may take up to 12 weeks for an infected individual to produce detectable HIV antibodies (i.e., the generally accepted "window period"), though some people will have a reactive result with third-generation HIV EIA tests as early as 20 to 30 days after exposure. This test is the most commonly used test in Canada. It's a combination test that detects both antibodies and the HIV p24 antigen. This test is more sensitive than the antibody test and can detect infection within 15 to 20 days. As many as 95% of people with HIV infection will test positiveFootnote * with a fourth-generation combination test within 34 days; however, the window period can be up to 12 weeks. HIV POC tests can be used to detect HIV antibodies. Results can be available in several minutes. Positive results from HIV POC tests are considered 'preliminary positive' only and should be confirmed with a standard serology test.

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Organization: Public Health Agency of Canada

Date published: November 2019

Window period: In most individuals, antibodies can be detected within weeks of HIV exposure. If the first HIV test is negative and a high-risk exposure occurred less than 12 weeks prior (i.e., during the window period), repeat HIV testing should be offered.

For more information, please consult your local public health laboratory or provincial/territorial guidelines.

Barriers and facilitators of HIV screening and testing

How healthcare providers can facilitate HIV screening and testing

Healthcare providers are encouraged to actively decrease barriers to HIV testing, so that individuals agree to seek testing. Those with negative results can take proactive attempts to protect themselves against HIV infection, and individuals with positive results can be linked to treatment and care.

Barriers to patients seeking HIV testing include:

To facilitate HIV testing, healthcare providers can:

Offering an HIV test

In Canada, HIV testing is voluntary: the client is free to accept or refuse the offer of testing. When offering an HIV test, healthcare providers should ensure the individual understands:

Note: Verbal consent is sufficient to proceed with testing. Although informed consent cannot be implied or assumed,
written consent is not necessary.

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