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26 years
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HIV test result is negative 8 weeks post exposure (4 weeks postPEP treatment). How much such results are accurate and conclusive , can they turn positive later on? and till when should i keep test ?
Oct 7, 2014
2nd opinion

Dr. Zakia Dimassi Pediatrics
Regarding HIV, you need to be aware of something called the window period, which is basically an interval period that varies between three weeks to six months between the time of HIV infection and the production of measurable antibodies to HIV seroconversion (seroconversion is when a specific antibody becomes detectable in the blood, and the corresponding antigen becomes undetectable. It is the point in time when the amount of antibody in the blood exceeds the amount of antigen, and the antibody becomes detectable. Before seroconversion, the antigen is detectable, but the antibody is not); during this time frame, antibody tests may give false negative (no antibodies were detected despite the presence of HIV) results. The majority of affected individuals develop detectable antibodies within an estimated 30 days after infection, although some seroconvert later. Most people (97%) have detectable antibodies by three months after HIV infection; a six-month window is extremely rare with modern antibody testing. During the window period, an infected person has the ability to transmit HIV to others although their HIV infection may not be detectable with an antibody test.
Antiretroviral therapy administered during the window period can delay the formation of antibodies and extend the window period beyond 12 months. Luckily, this does not apply to treatment with post-exposure prophylaxis (PEP). Those patients who have undergone PEP must take ELISA tests at various intervals after the usual 28 day course of treatment, sometimes extending beyond the conservative window period of 6 months.
Antibody tests may yield false negative results in patients with immune system diseases (such as X-linked agammaglobulinemia); other diagnostic tests should be used in such patients.
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