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If an HIV test was done using a chemiluminescent microparticle immunoassay (CMIA): does it mean that it screened for HIV 2 and/or is a 4th generation test?

On http://www.uphs.upenn.edu/bugdrug/antibiotic_manual/HIVtesting-newmethods.htm, it seems to hint that CMIA is only used for 4th generation tests but I am not entirely sure.

HIV blood antibody testing is used to diagnose HIV infection by using a two to three-tiered testing protocol. First, a 4th generation screening test for HIV-1and 2 antibodies, and p24 antigen is performed, using a chemiluminescent microparticle immunoassay (CMIA) (Abbott HIV Ag/Ab Combo Assay performed on the Abbott Architect instrument), or a 3rd generation immunochromatographic card (Trinity Biotech Unigold) assay is used. If positive, then a second test is done, using a rapid immunoconcentrating assay (Biorad Multispot).

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A detailed description of the “generations” of HIV testing by Alexander has been published.

Alexander TS. Human Immunodeficiency Virus Diagnostic Testing: 30 Years of Evolution.
Clinical and Vaccine Immunology. 2016;23:249-253. DOI: 10.1128/CVI.00053-16

https://cvi.asm.org/content/23/4/249

As described in Table 3 of this paper, a fourth generation HIV test is one that detects antibody to IgG and IgM HIV1 (including Group O) and HIV2 antibodies and HIV1 p24 antigen. The test is positive if HIV1 antibody, HIV2 antibody or HIV1 p24 antigen is detected but does not distinguish them.

The Abbott HIV Ag/Ab Combo Assay performed on the Abbott Architect instrument is a fourth generation HIV test that uses a chemiluminescent microparticle immune assay (CLMI) to detect the HIV1 and HIV2 antibodies and p24 antigen but does not distinguish between them.

To distinguish between HIV1 and HIV2 and p24 antigen, a second tier of testing is needed. This sequence of recommended testing is depicted well in Figure 3 of the article cited above. It is based on the most current CDC recommendations.

There are other fourth generation HIV “combo” tests (detect both HIV1 and HIV2 antibodies and HIV p24 antigen but don’t distinguish them) that use the chemoluminescent immune assays that are marketed by companies other than Abbott and use instruments other than the Architect . One of these is the ADVIA Centaur HIV Ag/Ab Combo assay (Siemens). There are others.

A 2013 publication describes the (complicated) technical details of several of the fourth generation HIV “combo” assays.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3562432/

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