HIV Window Period
Are your HIV tests accurate?
HIV testing may seem very complex.
This is greatly due to the testing ‘HIV Window Period‘. That irksome time from when a person is infected to when tests can actually detect a HIV infection.Click here to read about the Biology behind the Window Period
The HIV Window Period and Test Accuracy
HIV PEP Post Exposure Prophylaxis
This has caused a lot of doubt and worry with regards to the accuracy of tests done.
You might even be wondering right now how accurate your tests are.
There is a lot of confusing information out there. Some people claiming a window period of 2 weeks some people even saying 10 years!
This is because HIV testing technology has developed significantly since HIV was discovered in the 1980’s.
Also Read: When to Get HIV Test after HIV PEP
So a lot of information out there is out-dated.
Also, not the same standard of tests are available everywhere. This has caused different governments and different health authorities to develop different testing guidelines. So the reason why the Window Period is different in Massachusetts is different from Singapore is not because humans in the US react differently to HIV compared to humans in Singapore. It is because of local guidelines.
It depends a lot on WHICH TEST was done.
The following graph was prepared based on the latest information on Testing for the Diagnosis of HIV Infection.
Some points to note:
1. If you are within the first 10 days of possible HIV infection (aka the Eclipse Period), don’t bother doing any tests. There are NO tests that are accurate.
NB: If you are within the first 3 days of possible HIV infection please see us about PEP.HIV Prevention within 72 hours of exposure (PEP) – Click Here
2. At day 10, the HIV-1 RNA PCR can detect HIV Viruses in the blood.
Remember that the RNA PCR test has a high chance of giving a false positive result.
If the RNA PCR test gives a report of less than 5000 viral copies per ml, it is likely a false positive.Click here for information on HIV RNA testing at our Clinics
Also, the viral load may drop to an undetectable level upon full sero-conversion.
This is because the body’s immune system may have suppressed the infection to a point where there is not enough HIV virus in the blood for the RNA PCR test to detect.
3. Between day 14 to day 20, the HIV P24 Antigen will start appearing in the blood. This can be detected with 4th Generation tests (aka Combo tests).
This is why, although the official recommended Window Period for the Combo Test is 28 days, we are very confident when a patient tests negative at 2 weeks.
Remember that the P24 Antigen level will peak at about day 28 and becomes undetectable at about 6 weeks from infection.
This does NOT mean the 4th Generation (Combo) test is inaccurate after 6 weeks because the Combo test also detects IgM and IgG Antibodies (See below).Click here to learn more about the Combo Test at our Clinics
4. Between day 20 and day 23, the IgM Antibody starts to become detectable in the blood.
This is only detectable by 3rd and 4th Generation HIV tests.
This is the other reason why even though the 4th Generation (aka Combo) test is supposed to be conclusive at 28 days, at 3 weeks when a patient is negative, we tell him/her it is as good as conclusive.
5. Between day 28 and 48, the IgG Antibody starts to become detectable in the blood.
This is detectable by 1st, 2nd, 3rd and 4th Generation HIV tests.
This will remain detectable in the blood for as long as a person lives. Therefore, doing a Combo test not only detects HIV infections that occurred recently, it also detects infections from years ago.Click here for HIV Testing FAQ
More things to note:
The recommended 1st line screening for HIV infection is the Combo test NOT the antibody test.
So when you go for an HIV screening test, you should be asking for a Combo test. Take note that in Singapore the Combo test costs more than an antibody test.
Come see us for professional advice on which test you need to do.Click here to see the full range of our HIV/STD Services Click Here for Contact Details, Address and Opening Times. Click here to contact us
Call us at 63972095 now to book your treatment.
Feel free to email your queries, feedback and suggestions on what other topics you want to see in the comments section below.
Need more advice?
- Robertson Walk (Anonymous HIV Clinic) (+65 6238 7810)
- DUO Galleria (Bugis MRT) (+65 6976 5023)
- Novena Medical Centre (+65 6397 2095)
- Somerset – Orchard Building (+65 6262 0762)
- Raffles Place – PLUS (+65 6962 7144)
- Holland V (+65 6235 1339)
- Siglap (East Coast Road) (+65 6962 2144)
Where to find us – here
Selected clinics are open on Saturday and Sunday.
For lady patients who prefer female doctors, we have professional certified female Doctors to attend to your medical needs.
If you have any questions, visit our free online forum on sexual health, HIV and STDs.More on HIV symptoms.If you need a HIV test visit Our Clinics anytime during our opening hours. You do not need an appointment.Find out more about Anonymous HIV testing at our clinics.Can’t wait for 3 months to find out? Find out more about Anonymous Rapid HIV Combo test at our clinics.If you had a high risk exposure to HIV within the past 72 hours, you can take medicines to reduce your risk of actually contracting HIV. Find out more on HIV PEP Treatment.We are now open on weekends.Related Articles:HIV CMIA Test AccuracyHIV ELISA and ECLIA testGetting HIV from Oral SexMore on HIV symptomsHow long can HIV live outside the body?Erectile DysfunctionPremature Ejaculation
About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.