Is an eight week negative HIV test result conclusive?
The following is an actual conversation between an iCliniq user and a doctor that has been reviewed and published as a Premium Q&A.
The following is an actual conversation between an iCliniq user and a doctor that has been reviewed and published as a Premium Q&A.
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Patient's Query
Hello doctor,
I would like some advice, please regarding HIV testing. 10 days following a sexual encounter, (protected penetrative sex, unprotected oral sex) I was tested at my local GUM clinic. Although the lady from my encounter tested negative, mine came back as weakly reactive (fourth generation test). I retested which was now 21 days from the encounter and the result was exactly the same. The clinic sent some blood away for a viral load test which came back as negative/undetectable. Four and a bit weeks (eight weeks since the initial encounter) later, I returned for the follow-up blood test which, as I was advised, was weakly reactive again. This time the clinic sent some blood to a lab abroad for a confirmatory test which came back negative. What are your thoughts on this? Given that my results from the fourth generation test are the same over an eight-week period and viral load negative and whatever test they did abroad was negative should I be considered all clear? I cannot seem to shake this doubt that I have.
Hello, Welcome to icliniq.com.
I have noted your concern. After an indeterminate or weakly positive HIV screening test (usually due to cross-reacting antibodies), the second confirmatory test should be a different yet more specific test, such as a western blot. Western blot is 99.9 % specific, which means it reliably identifies 999 out of 1000 HIV-negative samples. A negative result on a confirmatory test reliably rules out HIV. So, you are HIV-negative. Can you enquire what the confirmatory test was? Was it a western blot?
Patient's Query
Hi doctor, Thank you for the reply.
I hope you can offer me further reassurance as I am going out of my mind with worry and stress still as I have had further tests since my original question. I am unsure what the test method was at the eight-week mark, but as it took seven days I am guessing it was the WB. Please see below my timeline of tests and results.10 days after - standard STD screening. HIV fourth generation test was 'weakly positive/reactive. 21 days after - I repeated an HIV fourth-generation test at the same clinic and the result was exactly the same. The doctor said that if I had had an early infection, this test would have more than likely been fully positive at this time and not the same as before. At this point, they sent my blood away for a test that detects the virus itself (viral load/PCR). This test came back as undetectable. 3.8 weeks after - repeated the same test (fourth generation) at the same clinic, which came back with the same level of reactivity as the previous test done almost five weeks prior. At this point, they sent my blood to a different lab for a confirmatory test (test method unknown). To my relief, this came completely negative. This test took around a week to come back. At this point, I considered myself all clear. 4.5 months after - I started to get really anxious again and stressed. So, booked into a private clinic where I tested negative on the HIV INSTI test. Given my test history, they also sent a sample of blood to have a lab test which I was told the next day needed further confirmatory testing. I believe they used the same fourth-generation duo test as all my others. So, I expected it to be reactive. However, later the same day, I was informed that the confirmatory test had come back as indeterminate. One out of the three categories was positive, whilst the other two were negative. Surely, if I had had HIV, the 8-week confirmatory test would have been positive, not negative? The 5-month Insti would have been positive, not negative, and whatever confirmatory test the private clinic did would have been positive, not indeterminate. Can it be that my blood just reacts to all the antibody tests and that I am just worrying myself stupid, or do you think that given my test history, I could be HIV positive? Would a PCR (Polymerase Chain Reaction) RNA (Ribonucleic acid) test be categorically conclusive at this point?
Hello, Welcome back to icliniq.com.
HIV INSTI (integrase strand transfer inhibitors)is a rapid screening test for antibodies against HIV-1 and 2. A negative test five months after a risky exposure conclusively rules out HIV. Moreover, discordant results on two different screening tests - weekly positive fourth-generation test (P-24 antigen and anti-HIV antibody test) and a negative result on HIV INSTI mean that your weakly positive screening test was most likely a false positive which can rarely happen due to antigen cross reaction. A positive screening test is anyways subjected to a confirmation Western blot before final diagnosis and only if WB is positive does it imply HIV infection. Not otherwise. RNA PCR is neither a screening test nor a confirmation test. It is commonly used for viral load monitoring in HIV positive patients. It can become positive early on in the infection and therefore has some role in early detection of HIV before the more reliable antibody-based test can be performed. However, even a positive RNA PCR is not conclusive and it has a high false positive rate of 5 % and therefore a positive test on RNA PCR is always followed up with more specific HIV antibody tests after three months (window period) for confirmation. HIV INSTI is one such rapid antibody-based test and a negative result at five months is 'conclusive'. Moreover, your earlier negative WB at eight weeks was already conclusive.
Regards.
Patient's Query
Hello doctor,
A couple of further questions, if I may. Given that the private clinic I went to after five months were able to do a confirmatory test the same day as the standard test, does this rule out that they used a WB test? I was under the impression that a WB is much more labor-intensive and took several days. Can I really feel confident in my negative status if after a negative Rapid-INSTI a more thorough lab test came back as indeterminate?
Hello, Welcome back to icliniq.com.
An HIV confirmatory test is usually a different test from the first one (screening). The type of test or testing technique is always mentioned in the test report, whether it was a western blot or a P24 Ag/Ab combo test. You can confirm from the lab, or else you may upload the test report here. As far as your HIV status is concerned, I think it is negative. It is impossible to imagine a scenario wherein an earlier weakly positive fourth-generation HIV screening test at 10 days, 21 days, and eighth week were finally interpreted as falsely positive by an eighth-week negative HIV confirmatory test to finally change to a scenario wherein a fifth month negative HIV INSTI test to be doubted as a falsely negative test by a confirmatory test. It seems impossible to detect both false positive and false negative HIV tests in the same individual at different times. I think a negative confirmatory test at the eighth week, a negative HIV INSTI test at the fifth month and a negative viral load PCR in the presence of a weakly positive fourth-generation HIV screening test altogether prove that you do not have HIV. RNA PCR should have detected circulating viral nucleic acid if the weakly positive fourth-generation HIV screening tests were true positives but it was reported as undetectable.
Regards.
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