The test which can detect HIV just 10 days after a sexual contact is, without a doubt, the test most people want to do.
It has the advantage that you do not have to wait out the normal three month window period to do an antibody test.
The launch of a combined antibody and p-24 antigen test brought this window period down to just 4 weeks but an HIV viral load test can reduce it even more.
How does it detect so early on and is it reliable? This amazing study says yes.
We know that once PCR was introduced to screen blood for transfusions, the terrible cases of people getting infected with HIV were reduced essentially down to zero. The reason for this, is that the test searches for the viral genetic material (RNA) and if it finds it, it makes milliones of copies to enhance detection by boosting a positive signal. It’s the same technique used to detect COVID.
And we know that the virus is not even growing in the first 3 days after infection. But then what is the point in time when we can say this detect has EXCELLENT detection rates?
According to this study, we can confirm definitively that 10 days after an infection, there are no cases that go undetected as long as the machine is capable of detecting 50 copies of the virus per millilitre.
The study is incredibly complex, looking at banked blood samples form before and after infection, testing this blood for HIV by PCR, applying statistical calculations, registering information about sex lives etc., but the most important findings are these:
- 10 days after a new infection the test will detect 100% of cases
- This is true when the machine can detect 50 copies /ml, that is to say, an exquisitely sensitive machine.
- The overwhelming majority of new HIV infections will get picked up BEFORE DAY 10
- The few cases that do not get detected are those with a low initial viral load at the moment of infection
- These low viral load situations happen when the transmission rate is low, for example in vagina-to-penis transmission.
- For this reason, I recommend waiting out the 10 day period before getting tested
The machines that we use in my laboratories detect around 100 copies/ml. Is that figure important in light of this study?
- In the vast majority of cases this threshold will be sufficient for HIV detection after 10 days of infection
- If we are extremely concerned, we can always wait a little longer or repeat the test with a different technique later on. Don’t hesitate to get in touch if you would like help with your own pesonal situation.
Bernhard P. Konrad, Darlene Taylor, Jessica M. Conway, Gina S. Ogilvie, Daniel Coombs,
On the duration of the period between exposure to HIV and detectable infection,
Epidemics, Volume 20, 2017, Pages 73-83, ISSN 1755-4365, https://doi.org/10.1016/j.epidem.2017.03.002.