Q. My fourth generation antigen-antibody test is negative. Is it necessary to do a retest?

Answered by
Dr. Sadaf Mustafa
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Dec 05, 2019

Hello doctor,

I had two sexual encounters with women whom I do not know their HIV status. Both were vaginal and a condom was worn. In the fourth and fifth weeks, I had a fourth-generation antibody-antigen test performed and it came back negative. Should I be retested again?



Welcome to icliniq.com.

It is a good idea to get repeat testing, here is why. The antibody testing at the fourth and fifth weeks can give you some idea of the HIV (human immuno deficiency virus) status, but the one at 12 weeks after the exposure will confirm the negative status completely. The reason being the window period.

The window period is a duration where a person can have HIV but still test HIV negative. The fourth generation is antigen-antibody based testing and the best we have so far for screening. When suspected acute HIV infection or high risk exposure, PCR (polymerase chain reaction) is the best in the fourth and fifth weeks post-exposure.

Of note, the window period for a fourth-generation antigen-antibody test is short as compared to other HIV tests available (about four weeks). Usually by this time, 95% of infection will be detected in the blood. In general, there is a three month window period for HIV after a given exposure, and therefore for the fouth generation testing to confirm that a person is more than 99.9% infectious. Hence the 12 weeks retesting is recommended.

I hope this helps.

Was this answer helpful?


Related Questions:
Please explain the accuracy of HIV Ag/Ab test at 40th day after exposure.

.. period of the Ag/Ab test varies from 18 to 45 days. Therefore a negative test at six weeks (42 days) would be considered conclusive in 98-99 % individuals. However, a negative test at 12 weeks is still considered the golden standard (conclusive in...   Read full

Are ELFA and HIV DUO tests conclusive at three and six months post-exposure?

I had a concern and checked my status of HIV through an ELFA test after three months of the last encounter ... I did another ELFA test after six months, and both were non-reactive ...   Read full

I fingered a lady and touched my penis with same hand. Am I at risk of HIV?

Should I get tested ... If yes, when is it ideal and what test should I go for ...   Read full

Also Read Answers From:

Also Read

COVID-19 Vaccines in India
Two vaccines, Covishield and Covaxin, have been granted emergency use authorization in India. Read about these vaccines'...  Read more»
Sinusitis - Causes, Symptoms and Treatment
Sinusitis is the infection of the air cavities within the nasal passages. Normally, the healthy sinuses are filled with ...  Read more»
Asthma and Its Rising Incidence
This article explains about asthma and its causes. It also focuses on the benefits of starting early treatment to lead a...  Read more»

Ask your health query to a doctor online?

Ask a General Medicine Physician Now

* guaranteed answer within 4 hours.

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website.