Expert: Kristen Brannock, MPH - 5/23/2005

Question
In January my Husband's 15 year old Daughter came to live with us.  Knowing she has been sexually active I took her for a full exam including and HIV test in March.  It was 8 weeks from the time she came here, I know she had not had sex during that time.
She says she had not had sex since Novemeber. Which would have been around four months. (if she is accurate on Novemeber being the right month)
The test was negative, how accurate are the results?
She had oral surgery today, and I am concerned with the family coming in contact with her blood, we are being careful, but I still worry.
Thanks.

Answer
It depends on the kind of test that was used. I suggest contacting the practitioner who administered the test to find out more about it. The ELISA test has a window period of 1-6 months, meaning that it can take the body up to 6 months to produce enough HIV antibodies to be detected by the test. The ELISA is the most commonly used test and it tests for HIV antibodies, not HIV itself. There is a new method being used in some states called blood pooling. This method has a much shorter window period of 2 weeks and tests for the actual virus.