HIV testing

The CDC recommends screening for HIV infection with laboratory based fourth generation HIV tests.

Fourth generation, immuno assays detect p24 antigen and HIV-1 structural protein that is detectable for 14 to 20 days after infection, and IgM and IgG antibodies to HIV –1  and HIV – 2, which appear 20 to 23 days and 28 to 48 days after infection, respectively.

HIV,RNA nuclear gastric testing detect HIV approximately 10 days after infection.

More than 99% of HIV infections in the US or HIV –1.

Fourth generation testing has the sensitivity of 62 to 80% in acute HIV, which is a phase early HIV infection in which there is a detectable viremia  by HIV RNA nucleic acid testing or p24 antigen but no detectable HIV antibodies.

Fourth generation testing has a sensitivity of up to 89% early infection, which includes the time in which anti-HIV antibodies become detectable. 

In established HIV, during which IgG antibody response is fully developed and a western blot test is reliably positive, fourth generation test, have a sensitivity and specificity of 99.5% to 100%.

False negative and indeterminate results with fourth generation tests have reported in patients infected with HIV while taking pre-exposure prophylaxis. 

False positive tests have been  reported in patients  with schistosomiasis, and Covid – 19, auto immune diseases and individuals who have received antigen receptor T cell therapies.

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