For many years there have been HIV tests capable of detecting the virus without waiting for the development of antibodies (which can take up to 3 months). There are private labs that offer this test – some say you only have to wait 3 days after risky contact, others mentioning 10 or 14 days. Obviously it is important to wait long enough to have a very robust result, so what is the true window period for HIV PCR testing?
This topic was studied in this article. It is a publication of the year 2017, but it is undoubtedly a study at the forefront of HIV diagnosis. It is tremendously difficult to interpret its results that are based on mathematical calculations, and even more difficult to turn it into practical advice for patients who want to do this test and want it to be the optimal moment, but I try to get the essence here… ..
(1) The virus barely reproduces in our bodies in the first 3 days after an infection. PCR tests are useless in this situation.
(2) PCR tests that are highly sensitive (capable of detecting very small amounts of the virus are what really make a difference. The vast majority of people will have a detectable viral load within the first week after contact.
(3) With these sensitive PCR techniques, there were no cases that could not be detected 10 days after the moment of infection. Less sensitive techniques may miss some cases within 10 days, and probably require 14 days or more.
(4) They are, then, a huge advantage in the early detection of HIV, but in high-risk cases, we would always recommend a second test using a more conventional technique, such as ELISA / antibodies, in recognition of the risk and seriousness of this disease.
Bernhard P et al. On the duration of the period between exposure to HIV and detectable infection, Epidemics, Volume 20, 2017, Pages 73-83, ISSN 1755-4365,