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Accuracy and Window Period of 4th Generation HIV Screening



I had exposure (mutual masturbation and titsex) with a sex worker two years ago. No oral, vaginal or anal sex took place. Oil was used on my penis and her breasts for lubricating. Half a year later I received a HIV screening (4th gen) along with my physical, which came back non-reactive. Should I retest due to possibility of false negative? I have read that in one case this person seroconvert after 4 years, although with obvious AIDS related symptoms


Hello and thank you for contacting the AIDS Vancouver helpline.

From my understanding, you are asking about the risk of HIV transmission during non-insertive masturbation and the accuracy of a 4th generation EIA test at approximately 6 months post exposure.

Non-insertive masturbation and foreplay (including tit sex) is considered to carry no risk of HIV tranmission. This means that there is no potential for transmission since all of the basic conditions for viral transmission are not present. In order to contract HIV the following conditions must be met:

  • There must be HIV present in a bodily fluid. The five bodily fluids that carry the HIV virus include: blood, semen (including pre-ejaculate), vaginal fluids, breast milk, and rectal secretions.
  • The bodily fluid containing HIV must have direct access to the bloodstream. This can be through cuts, tears, rips, mucous membranes, open sores, or needles.
  • Transmission occurs through a risky activity in which the first two conditions are met. For example: condom less sex, sharing needles, unsafe tattoos or piercings, vertical transmission–from mother to child (in utero, during delivery, breastfeeding).

Fourth-generation HIV tests can detect HIV infection in 50% of people by 18 days after infection; 95% of people by 34 days after infection; and 99% of people by one and a half months after infection. Fourth-generation HIV tests and the INSTI rapid test have a sensitivity of about 99.9%. In other words, if 1000 HIV-positive people were tested for HIV, 999 would test positive and one would incorrectly test negative. Since the vast majority of people who get tested for HIV are actually HIV negative, the chance of a negative result being false is extremely low.

In conclusion there is no need to be tested for HIV after the activity described. Since you already tested negative at the half year mark (well beyond the window period) there is certainly no need for a retest at two years.

Regards, AIDS Vancouver Helpline/Online, Dyson