What this test measures
This test detects antibodies the body produces against HIV-1 and HIV-2. Most labs use a third-generation enzyme-linked immunoassay (ELISA) that becomes positive 3–12 weeks after infection (window period). A reactive (positive) result must be confirmed with a second, different test (the WHO / NACO recommend a sequence of two or three different rapid / ELISA assays for diagnosis) — Western blot is no longer the standard confirmatory test in most testing algorithms.
Fourth-generation HIV-Duo (antigen + antibody combined) assays are now preferred because they detect HIV p24 antigen earlier (about 14–21 days after exposure), shortening the window period to 2–6 weeks. If you may have been exposed recently, ask for the HIV-Duo (4th-gen) test or HIV-1 RNA PCR.
Why it matters
India has the third-largest HIV epidemic in the world by case count, though prevalence has fallen substantially. NACO's National AIDS Control Programme provides free HIV testing at ~36,000 Integrated Counselling and Testing Centres (ICTCs) and antiretroviral therapy (ART) at over 600 ART centres nationwide — all confidential and free.
Early diagnosis is life-changing: with ART, life expectancy approaches normal, and undetectable viral load means HIV is untransmittable (U=U). Routine testing is recommended at least once for every adult, and more frequently for higher-risk groups (sex workers, MSM, transgender people, injecting drug users, prison inmates, partners of HIV-positive individuals, pregnant women — all pregnant women are tested under NACO's PPTCT programme). All testing in India is confidential by law.
How to prepare
No fasting or special preparation required. Standard venous blood sample. Counselling is recommended before and after testing (and is built into NACO's ICTC services). If you have had a high-risk exposure in the last 72 hours, post-exposure prophylaxis (PEP) — a 28-day course of antiretrovirals — can prevent infection if started promptly. If you may have been exposed in the last 6 weeks, request a 4th-generation HIV-Duo test or HIV-1 RNA PCR — they detect infection earlier than antibody-only tests.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| HIV-1 & HIV-2 Antibody (Reactive / Non-reactive)[1][2] | Non-reactive | Non-reactive (negative). If the test was within the antibody window period (3–12 weeks after possible exposure for 3rd-gen ELISA), repeat at 12 weeks for definitive result. A 4th-generation HIV-Duo test or HIV-1 RNA PCR can detect infection earlier. | Reactive — must be confirmed before any diagnosis is given. NACO recommends sequential testing with two or three different rapid / ELISA assays; only after confirmation is HIV reported as positive. If confirmed, the person is linked to an ART centre for free treatment under the National AIDS Control Programme. |
HIV testing options — window periods
| Test | What it detects | Window period after exposure | When to choose |
|---|---|---|---|
| HIV-1 & 2 Antibody (3rd-gen ELISA / Rapid) | Antibodies only | 3 – 12 weeks | Routine screening; confirmation testing |
| HIV-Duo (4th-gen Ag/Ab) | p24 antigen + antibodies | 2 – 6 weeks (14 – 45 days) | Recent exposure; pregnancy; blood-bank screening |
| HIV-1 RNA Qualitative PCR | HIV RNA | 10 – 14 days | Very recent exposure; neonatal diagnosis; early infection |
| Western Blot | Antibodies to specific viral proteins | After antibodies develop | Historical confirmatory test — largely replaced by sequential ELISA / rapid algorithm |
| HIV-1 RNA Quantitative PCR (viral load) | Virus quantity | After infection | Treatment monitoring — not for diagnosis |
Frequently asked questions
When should I get tested for HIV?
NACO and WHO recommend HIV testing at least once for every adult; more often (every 6–12 months) for higher-risk groups. Get tested after any potential exposure (unprotected sex, needle sharing, occupational exposure), in pregnancy (mandatory under PPTCT), before blood transfusion / organ donation, or if you have symptoms of acute HIV (fever, rash, lymphadenopathy 2–4 weeks after exposure).
Is HIV testing confidential in India?
Yes — both by law (HIV/AIDS Act 2017) and NACO policy. ICTC counsellors are bound by confidentiality. Results are shared only with the tested person (and parents / guardians for minors, with consent).
What is the "window period"?
The time between HIV exposure and when the test can detect infection. For 3rd-gen antibody tests — 3 to 12 weeks. For 4th-gen HIV-Duo (antigen + antibody) — 2 to 6 weeks (typically 14–45 days). For HIV RNA PCR — 10 to 14 days. A negative test before the window period closes does not rule out infection — retest at 12 weeks for definitive antibody result.
My test is reactive. Is it definitely HIV?
No — a single reactive screening test is not enough. NACO's testing algorithm requires confirmation with two more different assays. Only after the full algorithm is positive can HIV be diagnosed. False positives can occur in pregnancy, autoimmune disease, recent vaccination, and other conditions.
Is HIV testing free in India?
Yes — at all NACO-supported Integrated Counselling and Testing Centres (ICTCs) and government hospitals, HIV testing and ART are free. Private labs charge a fee for the test.
What is post-exposure prophylaxis (PEP)?
A 28-day course of antiretroviral drugs taken within 72 hours of a high-risk HIV exposure (occupational, sexual, sharing needles). It substantially reduces the chance of infection. Available at NACO ART centres and many hospitals. The sooner started, the better — ideally within 2 hours.
What is U=U?
"Undetectable equals Untransmittable" — a person on effective ART with sustained undetectable HIV viral load cannot transmit HIV sexually. This is backed by major international studies and is now part of NACO and WHO messaging.
Should I be tested in pregnancy?
Yes. NACO recommends HIV testing for every pregnant woman as part of the Prevention of Parent-to-Child Transmission (PPTCT) programme. If the mother is HIV-positive, ART during pregnancy and delivery reduces transmission to the baby from ~25% to under 2%.
Related HIV / STI tests
Tests commonly ordered alongside HIV - 1 & II, or that help interpret an unexpected result.
Sources & references
- NACO India — National HIV Testing Services Guidelines · accessed 2026-05-30T00:00:00.000Z
- WHO — Consolidated Guidelines on HIV Testing Services · accessed 2026-05-30T00:00:00.000Z
- CDC — HIV Testing Recommendations · accessed 2026-05-30T00:00:00.000Z
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