From the Guidelines
The first-line test for HIV is a fourth-generation immunoassay that detects both HIV-1 and HIV-2 antibodies and p24 antigen 1.
Key Characteristics of the Test
- The test has a high sensitivity and specificity, allowing for early detection of HIV infection 1
- It is typically performed on serum or plasma samples and can detect HIV infection as early as 14-22 days post-exposure 1
- A reactive result is then confirmed using a supplemental test, such as the HIV-1/HIV-2 antibody differentiation assay, to differentiate between HIV-1 and HIV-2 infections 1
Testing Algorithm
- The testing algorithm associated with the use of fourth-generation assays does not require Western Blot 1
- Instead, individuals with reactive results are further tested with an antibody immunoassay that distinguishes HIV-1 from HIV-2 antibodies 1
- If the differentiation assay is negative, further testing with a qualitative or quantitative NAAT is recommended to rule out acute HIV-1 infection 1
- If the differentiation assay is positive, viral load testing (and usually also CD4 determination) is recommended to direct management 1
From the Research
First Line Test for HIV
The first line test for HIV (Human Immunodeficiency Virus) is typically a fourth-generation enzyme immunoassay that detects both HIV antibody and p24 antigen, such as the Architect HIV Ag/Ab Combo Reagent Kit or the Vidas HIV Duo Quick 2, 3.
- These tests are designed to identify early HIV infections and have been used extensively worldwide for several years.
- They offer high sensitivity and specificity, with the ability to detect HIV-1 and HIV-2 infections.
- The VIDAS HIV DUO Ultra, a fourth-generation immunoassay, has demonstrated 100% sensitivity and 99.5% specificity overall, with a 99.7% specificity in low-risk individuals 3.
- These tests are useful for detecting early HIV infection, which is a critical phase for transmission, as the rate of transmission during acute HIV infection is higher than established HIV infection 2.