From the Guidelines
HIV Diagnosis Laboratory Tests
HIV diagnosis is typically made using a combination of tests, starting with a repeatedly reactive immunoassay followed by confirmatory Western blot or immunofluorescent assay 1.
- The initial test is usually a fourth-generation immunoassay that detects both HIV antibodies and p24 antigens.
- If the initial test is reactive, it is followed by a nucleic acid test (NAT) or a rapid HIV test to confirm the diagnosis 1.
- Western blot or indirect immunofluorescence assay can also be used as supplemental tests to confirm the diagnosis 1.
- Additionally, viral load tests, such as PCR or RNA assays, can be used to monitor the disease progression and treatment response.
- Rapid HIV testing may use either blood or oral fluid specimens and can provide results in 5 to 40 minutes 1.
- The U.S. Food and Drug Administration–approved tests for detection and confirmation of HIV infection include combination tests (for p24 antigen and HIV antibodies) and qualitative HIV-1 RNA 1.
From the Research
Laboratory Tests for HIV Diagnosis
The following laboratory tests are used for Human Immunodeficiency Virus (HIV) diagnosis:
- Fourth-generation assays that simultaneously detect HIV p24 antigen and antibodies 2, 3, 4, 5, 6
- Combination assays with separate results for anti-HIV antibodies and p24 antigen 2, 3
- HIV nucleic acid assays 3
- Western blot (WB) 3
- Viral load testing 3, 5, 6
- Dedicated HIV p24 antigen test 4
- CD4 count monitoring to estimate the stage of infection and suggest a therapeutic approach 6
Characteristics of Fourth-Generation Assays
- Reduce the diagnostic window between infection and diagnosis 2, 4
- Improve detection of acute HIV infection 3, 5
- Have high sensitivity and specificity 3
- Can detect diverse HIV subtypes 5
- Have similar breadth of reactivity and diagnostic utility across different commercially available assays 5