Clarification URGENTLY needed re subtype B
Jul 5, 2010
Hello Dr Bob - I live in the UK - could you just clarify for me that the HIV test used in the UK tests for subtype B? The reason I ask is that I read this online and it has perplexed me: EIA tests which can detect either one or both types of HIV have been available for a number of years. According to the US Centers for Disease Control and Prevention, current HIV-1 EIAs "can accurately identify infections with nearly all non-B subtypes and many infections with group O HIV subtypes." Maybe I'm being an imbecile but does this mean that the tests don't look for subtype B (which I thought was the most common)? I have looked in the archives but am still confused. Thankyou so much for your help!
Response from Dr. Frascino
Yes, all routine HIV-antibody tests test for subtype B. The nomenclature can get a bit confusing at times.
Here's the scoop. HIV-1 is divided into subtypes designated A through K and collectively referred to as Group M. In addition to Group M subtypes A, B, C, D, E, F, G, H, I, and K, there are about 15 circulating recombinant forms (CRFs). Six strains account for most HIV infections: A, B, C, D, and CRFs -- CRF01-AE and CRF02-AG. Another group of viruses is labeled "N" for "new." They were first reported in 1998. Group O (for "outlier") shows about 55-70% homology with the M subtypes. The O and N groups are now thought to represent divergent evolution or distinctive cross-species transmission. Over 98% of HIV-1 infections in the US are caused by subtype B. Most non-B subtypes in the US were acquired in other countries. The rare O and N viruses are found primarily in West Africa. See, I told you the nomenclature was a bit confusing! The important thing to realize is that standard serological tests (routine HIV-antibody tests) detect M subtypes (A-H) of HIV-1 and some tests detect HIV-2. EIA screening tests may fail to detect O and N subtypes; however, these strains of HIV are extremely rare in the US. Only two patients with strain O HIV infection were detected in the US through March 2000. There were no recognized infections with the N strain in the US through March 2000.
Hope that helps clarify the situation and puts your concerns to rest. The statement you read pertained to current EIAs being able to pick up non-B subtypes in addition to the usual Group M (subtypes A-H).
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