| Type of test | Target of detection | Approximate time to positivity following infection (days) | Additional information |
| Tests used for initial screening |
| HIV antigen/antibody tests | IgM and IgG antibody to HIV-1 and HIV-2 p24 antigen | Laboratory-based test: 18 to 45 Point of care: 18 to 90 | - Improved sensitivity for detecting acute infection compared with antibody-only tests.
- Laboratory and point of care-based tests are available. Most laboratory tests are immunoassays. Point of care tests use lateral flow technology and are not as sensitive.
- This test does not differentiate between HIV-1 and HIV-2.
|
| HIV antibody only (ELISA) | IgM and IgG antibody to HIV-1 | 23 to 90 | - Laboratory and rapid tests available. An FDA-approved self-test also available.
- Laboratory-based tests usually able to detect virus sooner (eg, 20 to 30 days).
- Positive results require confirmation with the laboratory-based antigen/antibody assay.
|
| Confirmatory tests |
| HIV-1/HIV-2 differentiation assay | Antibodies to HIV-1 and/or HIV-2 antigens | 23 to 90 | - This is a rapid laboratory-based test used to confirm a positive antigen/antibody combination assay.
- It can distinguish between HIV-1 and HIV-2 infection.
|
| Western blot | IgG antibody | Indeterminate result: 35 to 50 Positive result: 45 to 60 | - Test results often take several days to weeks to return.
- Detects IgG antibody to HIV-1 proteins.
- Does not reliably detect HIV-2 or subtype O HIV-1 virus.
- No longer offered by most labs.
|
| Nucleic acid tests |
| Qualitative tests | HIV RNA | 10 to 33 | - Approved by US FDA for diagnosis of HIV-1.
- Typically reserved for evaluation of possible acute HIV infection or as part of HIV screening for blood donors or individuals being evaluated for or taking HIV PrEP (especially injectable PrEP).
|
| HIV DNA | 10 to 33 | - Not intended for initial screening or routine testing of adults.
- Reserved for evaluation of indeterminate test results, particularly in setting of risk factors for HIV.
- Should generally be ordered after consultation with an HIV specialist.
|
| Quantitative tests | HIV RNA | 10 to 33 | - Used to quantify HIV-1 RNA or HIV-2 RNA from plasma samples. HIV-2 RNA quantification assays only available from specialized laboratories in the United States.
- Primarily used for monitoring response to treatment in persons with HIV-1.
- Used to help assess for acute HIV infection in patients with symptoms of acute (primary) HIV or with laboratory results suggestive of acute HIV (eg, symptoms of acute HIV plus negative or indeterminate antigen-antibody tests, or positive antigen-antibody test with negative differentiation assay).
- Not intended for initial screening or testing of adults, unless the person is receiving PrEP (particularly injectable PrEP).
- Quantitative tests are more readily available than qualitative tests. In addition, they are generally preferred if concern for acute HIV infection since they give an HIV RNA level that serves as pre-treatment baseline.
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