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Dr. Andrew Rynne
MD
Dr. Andrew Rynne

Family Physician

Exp 50 years

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How Accurate Are These Tests?

hi doctor,i had sex with a woman,and the condon break.i know that she was hiv p.i did a test 9 days later,it was negative.another test 20 days later with antibody hiv 1/2 and p24 antigen,it was negative.another test 70 days later for hiv 1/2 antibody,also negative.how acurate are those test?
posted on Fri, 14 Mar 2014
Twitter Tue, 29 Apr 2014 Answered on
Twitter Tue, 29 Apr 2014 Last reviewed on
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Infectious Diseases Specialist,  's  Response
HIV infection is diagnosed by detection of antibodies against HIV or viral antigen (p24 antigen) or viral DNA or isolation of virus. All of these tests are reliable and accurate.

There is something called a "window period" in diagnosis of HIV infection. It is usually about 6-8 weeks. During this period the person is HIV infected, but, the tests come negative.

The test that was performed in your case at 20 days is a 'Fourth generation HIV kit' which can detect HIV p24 antigen and HIV antibodies concurrently. The "window period" with this test is about 2 weeks i.e. 14 days; so if you were detected HIV negative at 20 days you are safely HIV negative. This is further confirmed by the test taken at 70 days.
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How Accurate Are These Tests?

HIV infection is diagnosed by detection of antibodies against HIV or viral antigen (p24 antigen) or viral DNA or isolation of virus. All of these tests are reliable and accurate. There is something called a window period in diagnosis of HIV infection. It is usually about 6-8 weeks. During this period the person is HIV infected, but, the tests come negative. The test that was performed in your case at 20 days is a Fourth generation HIV kit which can detect HIV p24 antigen and HIV antibodies concurrently. The window period with this test is about 2 weeks i.e. 14 days; so if you were detected HIV negative at 20 days you are safely HIV negative. This is further confirmed by the test taken at 70 days.