An additional HIV test should be offered to all persons at 3 months (12 weeks) to definitively exclude HIV infection.” – BASHH ( emphasis mine) They should be offered a 4th generation laboratory HIV test and advised that a negative result at 4 weeks post exposure is very reassuring/highly likely to exclude HIV infection. “Patients attending for HIV testing who identify a specific risk occurring more that 4 weeks previously, should not be made to wait 3 months (12 weeks) before HIV testing. The British Association for Sexual Health and HIV (BASHH) has this to say concerning the conclusiveness of the 4th generation HIV Antigen/Antibody Combination laboratory test, taking into account that the rapid HIV Combo/Duo test is perhaps less accurate than its laboratory equivalent:
The UK Guidelines recognize the disadvantages of rapid POCT where there is “reduced specificity and reduced sensitivity versus current fourth generation laboratory tests.” In other words, these rapid tests have somewhat lesser accuracy compared to 4th generation laboratory HIV tests.
outside conventional healthcare settings and where a delay in obtaining a result is a disadvantage, but these must be weighed against the disadvantages of a test which has reduced specificity and reduced sensitivity versus current fourth generation laboratory tests.” – UK National Guidelines for HIV Testing, page 9 “They have advantages of ease of use when venepuncture is not possible, e.g.
But the committee has this to say concerning rapid point of care tests (POCT) e.g. It is true that the UK Guidelines recommend the HIV Antigen/Antibody combination test (HIV Combo/Duo test) as a first-line assay. So do the “ UK National Guidelines for HIV Testing” advise that a rapid HIV Combo test is conclusive at 28 days after exposure? Compared to older 3rd generation tests where the window period for detecting Immunoglobulin M (IgM) antibodies can be anywhere between 20 to 23 days, 4th generation tests effectively reduce the window period by about 1 week. These 4th generation HIV tests can detect the p24 antigen as early as 14 days after a high-risk exposure (for example, a needle stick injury or unprotected sexual intercourse with a high-risk partner). Unlikely previous HIV tests that only test for antibodies that our bodies produce to the invading HIV virus, 4th generation tests are also able to detect p24 antigens present on the surface of the HIV viral particle. As Alexander Pope has correctly observed, “A little learning is a dangerous thing.”įirstly, what exactly is this 4th Generation HIV Test? While it’s true that the World Wide Web has some good information on various topics, sometimes the overwhelming amount of information might actually be confusing at best, and perhaps even deleterious to true knowledge at worst. I remember a limerick while I was in primary school – complete with frizzy hair and an oversized shorts – that reads: “Doctor, there is a website that claims that according to the UK guidelines, the rapid HIV Combo/Duo test is conclusive on day 28. “Doctor, I’ve browsed many websites locally, and some advised that the rapid 20 minutes HIV Combo test is definitely conclusive at 28th days after my last high risk exposure. “Doctor, is my result conclusive at 28th days post-exposure?” This test is also known as the “rapid HIV combo test,” the “rapid HIV Duo test,” or more correctly, the “rapid p24 antigen/HIV-1 and HIV-2 antibody combination test.” My patients have often asked me the following questions concerning the rapid 4th generation HIV test so readily available in Singapore’s clinics.
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