From the Guidelines
If an individual has a positive Human Immunodeficiency Virus (HIV) 1 and 2 antibody test but is HIV negative, they will not always be positive for HIV 1 and 2 antibody, as false positive results can occur due to various factors and subsequent tests may return negative results.
Understanding False Positive Results
False positive HIV antibody tests can occur due to several factors, including:
- Cross-reactivity with other antibodies from conditions like autoimmune diseases
- Recent vaccinations
- Technical laboratory errors As noted in the guidelines for the management of persons infected with HIV, a positive or reactive screening test result is confirmed by Western blot or indirect immunofluorescence assay 1.
Importance of Confirmatory Testing
It is crucial to undergo confirmatory testing such as an HIV RNA test (viral load) or Western blot to determine the true HIV status, as these tests look for the actual virus rather than just antibodies and provide more definitive results 1.
Recommendations for Testing
If confirmatory tests are negative, the individual is considered HIV negative regardless of antibody test results. Regular retesting may be recommended in certain situations to ensure continued accuracy of the HIV status, especially if risk factors are present, such as high-risk behaviors or exposure to HIV 1.
Key Considerations
- The presence of STDs indicates recent high-risk behavior and increases the risk of HIV transmission to others
- HIV-seronegative persons perceived to be at risk should be counseled regarding the risk of acquiring HIV infection
- Screening for high-risk behavior can be accomplished by a brief series of questions administered by questionnaire in the patient waiting room by the health care provider or by other personnel in the health care setting 1.
From the Research
HIV Antibody Test Results
- An individual with a positive Human Immunodeficiency Virus (HIV) 1 and 2 antibody test but is HIV negative may not always be positive for HIV 1 and 2 antibody, as the results can vary depending on the test used and the stage of infection 2, 3, 4.
- The sensitivity and specificity of HIV antibody tests can differ, with some tests detecting antibodies earlier or more accurately than others 2, 5, 6.
- False-negative or indeterminate results can occur, especially in early stages of infection or with certain tests 3, 5.
Test Variability and Limitations
- Different tests, such as antigen/antibody immunoassays, antibody-based rapid tests, and antigen/antibody rapid tests, have varying sensitivities and specificities 2, 6.
- The use of Western blot as a confirmatory test can also have limitations, including indeterminate results and the need for technical expertise 3, 4, 5.
- Alternative supplementary tests, such as anti-HIV antibody titer, can be used to support diagnosis, but may not always be reliable 5.
Diagnostic Challenges
- Detecting acute HIV infection can be challenging, as antibodies may not be present, and p24 antigen and RNA tests may be needed 6.
- The choice of test and interpretation of results require careful consideration of the individual's clinical presentation, risk factors, and test performance characteristics 2, 3, 4, 5, 6.