Can I have peace of mind with a negative NAT test result?
Q:
I was tested by the Anti-HIV (antibody) test and by NAT 11 days after placing myself at risk. The antibody test result was negative and the NAT test result was also negative. How confident can I be in the test results, especially if the NAT result was negative? Do I need to be tested again?
by Greg
19 Jun 2012
Greg 19 Jun 2012
A:
Thank you for your question
If you did not had any risk behavior, such as unprotected sex, within 5 days before you had the NAT test and no risk behavior since you were tested, you can be confident in the NAT test result.
For all readers:
The window period of HIV infection is between 2 to 12 weeks after the virus enters the body. The tests most commonly used to detect infection look for antibodies, a type of white blood cells that fight HIV. It can take the body up to 12 weeks after infection to produce a sufficient quantity of these cells for testing. Some people will produce a sufficient quantity of antibodies only 2 weeks after infection. In others, it may take 6 to 12 weeks for the body to produce a sufficient quantity of antibodies. Because of this, the Ministry of Public Health in Thailand has set the window period for HIV infection at 12 weeks to ensure the highest confidence in the test results. If you test for HIV within the window period, it will be recommended that you test once again at the end of the period. It is important that you do not have any additional risks during this period in order for the test results to be accurate.
We understand that waiting for several days to months after having a risk can lead to stress. Thus there is a test that detects HIV infection in a shorter period of time. This test can detect HIV from 5 days to 2 weeks after any risk. This test is known as NAT and it detects copies of HIV instead of the white blood cells that fight HIV (antibodies). Currently NAT testing is only available at the Thai Red Cross AIDS Research Centre.
