HIV Screening (ELISA / Rapid Test)
HIV screening tests detect antibodies against HIV-1 and HIV-2 and, in fourth-generation assays, also the p24 antigen. A positive screening test is always confirmed with a second method (a different ELISA or Western blot) before HIV infection is diagnosed. In India, the National AIDS Control Programme (NACO) recommends a three-test strategy for HIV diagnosis. Early diagnosis and antiretroviral therapy transform HIV into a manageable chronic condition with normal life expectancy.
Expected Result
Normal
Non-reactive
Any reactive result must be confirmed by a second different assay before HIV is diagnosed.
This is a qualitative test — results are reported as positive or negative rather than as a numeric range. Interpretation may vary by laboratory method; always review with your doctor.
What a Negative Result Means
A non-reactive HIV screen more than 3 months after a potential exposure effectively rules out HIV. Fourth-generation tests detect infection as early as 2–3 weeks after exposure. If exposure was very recent (within a month), repeat testing at 6 weeks and 3 months is standard. In ongoing risk situations, periodic testing is recommended every 3–6 months.
What a Positive Result Means
A reactive HIV screen requires confirmation — a single reactive test is not a diagnosis. Confirmation uses a different ELISA assay or Western blot; the NACO algorithm uses three different rapid tests. A confirmed positive result triggers CD4 count, HIV RNA (viral load), genotype for resistance, and immediate start of antiretroviral therapy. Modern treatment restores immune function and reduces transmission risk to essentially zero with undetectable viral load.
Frequently Asked Questions
How long after exposure should I get tested for HIV?
Fourth-generation tests (detecting p24 antigen plus antibodies) turn positive 2–3 weeks after exposure in most cases. For highest certainty, test at 3 weeks, 6 weeks, and 3 months after a known exposure. A negative test at 3 months with no further exposure is considered definitive.
What if my HIV screen is reactive?
A single reactive screen is not a diagnosis. Confirmatory testing (a second different assay, ideally two) is always done. If confirmation is positive, you will be started on antiretroviral therapy which is now a single daily pill for most people, suppresses the virus to undetectable levels, and allows normal life expectancy. Counseling and partner notification support are part of the process.
Can I transmit HIV if I am on treatment?
If you are on effective antiretroviral therapy with an undetectable viral load for at least 6 months, the risk of sexual transmission is effectively zero — this is the Undetectable = Untransmittable (U=U) principle, supported by multiple large studies. Consistent adherence to medication is essential. This also applies to mother-to-child transmission, which is prevented with treatment during pregnancy, delivery, and breastfeeding.
Related Infectious tests
See all →ASO Titre (Anti-Streptolysin O)
Antibody against streptococcal toxin — evidence of recent strep infection.
IU/mLInfectiousWidal Test
Antibody test for typhoid fever — used cautiously due to specificity issues.
InfectiousDengue NS1 Antigen
Early dengue virus antigen — detectable in the first week of fever.
InfectiousDengue IgM Antibody
Antibody that rises in the second week of dengue infection.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
Read Full Medical Disclaimer →