Q&A HIV | DrSafeHands
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Is HIV 1, 2, and p24 combo CMIA test index value of 0.05 (negative) reliable at 20 days post-exposure? Do I need to retest at 30 or 45 days?

Answer requested by Tushar Mittal

Hi Tushar.

Thanks for your query.

The HIV 4th gen test is considered highly accurate after 28 days of potential exposure. After 45 days, as per CDC guidelines, it can be taken as conclusive.

To answer your specific query, the p24 antigen becomes detectable in the blood after 2 to 3 weeks, in case there is an infection. So, at 20 days getting a negative result should be a huge morale booster.

For conclusive results, just give one more sample after 45 days of potential exposure. If you can not wait for that long, just give a sample after 28 days. A negative result would mean you are very safe. And then you may repeat anytime after 45 days, to follow the protocol and have conclusive results.

Hope this helps.

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I took the 4th generation HIV combo test 25th day from exposure. Is it negative conclusive?

Answer requested by Uday Prakash Singer

The HIV fourth-generation test looks for p24 antigen along with antibodies to HIV 1 and HIV 2. This is considered highly accurate after 28 days and is taken as conclusive after 45 days of suspected exposure.

In your case, the test is negative after 25 days; therefore, you are reasonably safe and must not worry.

As per protocol, it is advisable to repeat the test after 45 days.

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Is the collection of HIV serology taken blood from a vein after 7 weeks conclusive?

Answer requested by Ziyad Sabai

HIV serology test that looks for antibodies to HIV I and II, also called the third generation test is considered conclusive after twelve weeks of suspected exposure. If the test is a fourth-generation test, which looks for p24 antigen and antibodies to HIV I and II, it is considered conclusive after 45 days of suspected exposure. The 4th gen test is highly accurate even after 28 days and someone testing positive after the 28th-day 4th gen test has returned negative is very rare.

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Can 5 HIV non-reactive tests some within the widow period and some after 90 days considered conclusive by all protocols?

Answer requested by Garba

The screening test for HIV that depicts antibodies to HIV I and II are considered conclusive after 90 days of suspected exposure as per the existing protocols. An only exception is a person who has taken post-exposure prophylaxis or PEP within 72 hours of high-risk exposure. In such a scenario, the test is considered conclusive after 6 months of exposure. However, a negative test or a non-reactive test after 3 months, in case a person has taken PEP is highly indicative of the person being not infected.

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