Understanding HIV Test Accuracy: A Parent's Guide

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 November. Which would have been around four months. (if she is accurate on November 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
Hi,
A single HIV test that is negative does not mean that she doesn't have the disease. In order to be sure, she needs to abstain from ANY sexual behavior for 6 full months and be retested. If it is again negative then she is clear. Once she again has sex then risk of contracting HIV starts all over again.