Is a retest needed despite a negative Western blot at 16 weeks?

Question

Hello doctor,

My doctor has recommended Western blot for human immunodeficiency virus (HIV-1 and HIV-2) as a screening test. The RIBA (Recombinant Immunoblot Assay) test was negative for HIV after 16 weeks of exposure. I also had a negative CMIA (chemiluminescent microparticle immunoassay) test after 12 weeks post exposure.

The hepatitis and STD (sexually transmitted disease) panel are also negative. Is a negative Western blot 100% accurate and reliable at 16 weeks post-exposure? If Western blot is so accurate, why is it not used as a screening test? Is a six-month retest required despite a negative Western blot at 16 weeks? Which generation is RIBA, and how accurate is it as a stand-alone screening test? Will a recent CMV (cytomegalovirus) affect these test results' accuracy?

Please help.

Answer 1

Hi,

Welcome to icliniq.com.

Western blot is a highly sensitive and specific test, which is run after a repeatedly reactive ELISA (enzyme-linked immunosorbent assay) or HIV (human immunodeficiency virus) rapid test. The Western blot test is not used as a diagnostic test in the absence of an initial positive screening test, due to the rare possibility of false positives. It is a confirmatory test and not meant as a primary test and carries value in confirming a positive rapid test or ELISA. You can be 100% certain if a Western blot has been performed at 16 weeks post-exposure and is giving a negative result that you do not have HIV.

Rapid tests or ELISA (enzyme-linked immunosorbent assay) are almost always used as the first screening method. These are inexpensive and at the same time highly sensitive for detecting the presence of HIV antibodies. The rapid kits, which are now available, give an accurate result.

As per the testing guidelines, a repeat HIV test should be provided to all individuals who have tested HIV negative but where a possible exposure has occurred within the window period. Window period refers to the time after infection and before seroconversion, which means markers of infection (HIV-specific antigen and antibody) are still absent or too low to be detected by the test. There is natural variation in this period, and it is difficult to make for a particular person.

A negative test at 12 weeks definitely excludes HIV infection, had there been no other exposure. Your negative HIV test results are very encouraging, but if you had exposure, and as per recommendations, I advise you to undertake an HIV antibody test at six months of exposure.

HIV proteins used in western blot can be produced by recombinant DNA (deoxyribonucleic acid) in a technique that is called RIBA (recombinant immunoblot assay). It is categorized as an HIV third-generation test. Yes, a recent CMV (Cytomegalovirus) infection, and for that matter, any acute illness can interfere with the results.

I hope your queries are answered, but if you still have any more questions, please revert.