Exactly 30 days post exposure (unprotected vaginal/oral sex) I had a rapid test done. It came with a faint line and then confirmed with a confirmatory test Western Blot. The results were indeterminate with no information about viral bands detection. The case manager who informed me about the test results explained that WB could come indeterminate if I was at the early stage of the infection and was still seroconverting or non-specific antibody reaction. She also said that if I had a cold virus at a time it could've caused the antibody test to show inconclusive results.
Are there any other reasons besides seroconversion, other autoimmune diseases and viral infections for Western Blot to show indeterminate?
I know that according to the CDC guidelines 3 month-mark is considered considerate, however, what if the patient is consistently indeterminate on the Western Blot? Does it mean I am negative or should I try other tests?
Thanks in advance for any answer.
Hi there and thank you for contacting the AIDS Vancouver Helpline.

I understand that you have questions about the indeterminate results obtained from Western Blot test. You mention that you have conducted the test at the 30 day post-exposure mark.

I would like to start by saying that the answer you received from your case manager is highly accurate and will be no different from mine. I will try to simplify the answer and help you make some sense of the bigger picture.

Western Blot and Rapid tests both look for antibodies that our bodies develop against an HIV infection. Most people develop detectable antibodies in 21-25 days post-infection. As your case manager have mentioned, one explanation for why your test results came back indeterminate is that your body might not have fully developed antibodies (incomplete pattern). This may be the case especially if you were in the early stage of seroconversion (acute HIV infection).

Another possibility, which was also mentioned by your case manager, is that the Western Blot test was picking up on another retrovirus that you are infected with (such as the flu virus). Since both HIV and flu viruses are retroviruses, a cross-reactivity to the proteins of that other retrovirus may have occurred.

The state of your immuno system as well as the sensitivity of the kit used for testing could also be contributors to the indeterminate test results.

I understand that receiving indeterminate results can be stressful as it hinders the decision making process and could contribute to the anxiety you are experiencing in regards to your HIV status. That said, your case manager sounds very knowledgeable of the test conducted and its shortcomings. The Western Blot is considered the "golden standard" in HIV testing. If Western Blot test results are indeterminate, it is advised that a confirmatory PCR NAAT test is conducted to confirm the infection.

You are encouraged to continue your communication with your case manager and/or doctor. Remember that all tests that are conducted at or after the 3 month (12 weeks/84 days) post exposure are considered conclusive. At that mark, all tests should be able to detect antibodies developed against the virus and/or the genetic material of the virus itself.

I trust that I have answered your question. For additional information on HIV risk, testing and prevention, feel free to visit our website at

In health,




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