When should a person be tested for HIV? How long is the purported “Window Period” for testing?
Comedian Chris Rock once said that, “the scary thing about the AIDS test is that when you take it, you don’t get the results back for FIIIVVEE days.”
But, the really scary thing about HIV tests is not waiting for the results for five days, but doing the wrong test at the wrong time. You might be getting a false and unreliable result if that is the case.
If you are concerned about your HIV status, or if you are thinking of doing a HIV test, you should discuss with your doctor about the different HIV tests available, and the associated window period for the various tests.
What exactly is the Window Period?
Suppose a person exposes himself to a source of HIV infection, such as a needle-stick injury or an unprotected sexual encounter, the HIV virus might be introduced into his blood stream.
When this person becomes infected, HIV multiplies in the blood and the person’s body develops antibodies against the HIV virus.
The “window period” is the length of time after initial infection and exposure. It is the period of time required for the virus to become detectable by HIV diagnostic tests. The duration of the window period varies depending on the type of diagnostic test used and the method it employs to detect the virus.
The window period usually varies from person to person. It is extremely rare for an HIV-infected person to develop antibodies after 3 months of a potential exposure. Antibodies usually develop within 3 months.
A person who tests negative for HIV antibodies 3 months after an exposure usually does not require further HIV testing, not unless he or she has had repeated exposures to HIV during the 3 months period.
Which test should I do? A brief summary.
In a nutshell, if you have exposed yourself to HIV, there are no tests that will be anywhere near accurate at days 0 to 9. Don’t bother doing a HIV test during this time.
If you have exposed yourself, and if it’s still within the first 72 hours (3 days), you can speak to your doctor concerning HIV Post Exposure Prophylaxis (HIV PEP), which can lessen your chances of being infected by the virus, but this is not 100% effective.[1] HIV PEP is most effective if commenced immediately after the exposure.
From Day 10 onwards, your physician might order a HIV RNA PCR test to see if there are viral particles detectable in your blood.
The best time for the 4th generation HIV tests to detect the HIV p24 antigen is between 20 to 30 days after exposure.
At 30 days (1 month) after exposure, your doctor might also consider the 3rd generation HIV tests to detect HIV antibodies in your blood. A negative test result at this time is highly reassuring, but not conclusive. This test should be repeated at 90 days (3 months) after exposure to definitively exclude a HIV infection.
If you are allergic to technical details and microbiology, I would advise you to stop at part 1 of this article. That is probably all you need to know when you consult your doctor.
But if you are curious, and would like to know why I wrote what I wrote, by all means continue with part 2 of this article.
You have been warned.
Footnotes
[1] A multicentre, case-control study of 712 health care workers exposed to HIV demonstrated that the use of zidovudine prophylaxis reduced the odds of HIV infection by 81%. See Cardo DM, Culver DH, Ciesielski CA, Srivastava PU, Marcus R, Abiteboul D, et al. A case-control study of HIV seroconversion in health care workers after percutaneous exposure. Centers for Disease Control and Prevention Needlestick Surveillance Group. N Engl J Med 1997;337(21):1485-90. It has been suggested by HIV experts that the latest HIV PEP regimes could have better effectiveness.
