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how reliable is the 4th generation test in the 4th week of exposure?

Question: 

Hello, I had unprotected sex with a guy and I was very concerned if I got infected with hiv, so I got tested 4 weeks later with the 4th generation test and It was negative. Can I be relieved with the result.

Answer: 

Hello,

Thank you for your inquiry. From what we gather from the question, you were asking about the reliability of 4th Generation EIA tests after 4 weeks, commonly referred to as "combination," "COMBO," or "DUO." The antigen (ag) test- P24 is detectable immediately after infection, & only for the first few weeks. The antibody (ab) test has a window period of 4-12 weeks. Most HIV specialists consider this "DUO" test conclusive at 6 weeks. The "DUO" test is considered to be highly accurate. Official HIV testing guidelines still recommend re-testing at 12 weeks for completely conclusive results. In addition, after 4 weeks >95% of infected individuals will have detectable antibodies and will have a positive result with a 4th Generation enzyme immunoassay test. [1]

If you have any further concerns or questions, please consult your physician.

Reference for interest: 1. https://www2.gov.bc.ca/assets/gov/health/about-bc-s-health-care-system/office-of-the-provincial-health-officer/hiv-testing-guidelines-bc.pdf

Regards,

AIDS Vancouver Helpline/Online, Sara