The CMIA HIV test is a combined antibody/antigen test that is 95% accurate by 6 weeks and would give you a final result at 3 months. Having a negative test at 84 days is an excellent sign as the test would be 99% accurate by that time. I would be surprised if a HIV antigen/antibody test did not have some reactivity showing by this time. If you wanted to remove any doubt at all particulary if this was a one time event and you want closure. You could always do another test after the 3 month/ 90 day period, but I would be very surprised if the results changed.
There are many different HIV tests around the world that use different testing technology to look for HIV. To get the best information about your HIV tests window period, I would recommend asking the people that are doing your test as they would have the details about the test they use.
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