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Together the tests have a sensitivity and specificity of > 99% at 12 weeks post-exposure.Once an individual has been exposed to HIV it can take up to 12 weeks for the body to make antibodies that are detectable by this test. This means that any exposure that occurred within 12 weeks prior to the EIA are not detected. This is referred to as the window period, and if there was an exposure during that time, the individual would need to be retested. The EIA is the first test to be completed on the serum. If the EIA comes back positive andonly if this test is positive, a western blot will be completed by the laboratory to confirm the EIA results. All positive EIA tests must be confirmed with a western blot.If the EIA is negative, then the western blot is NOT completed, and the person is considered to be HIV negative.If the EIA is positive and the western blot is negative, then the individual is HIVnegative.If the EIA is positive and the western blot is positive, then the individual is HIV positive. If the EIA is positive and the western blot is indeterminate,othe person may be in the process of 3 seroconverting,omay have received an HIV vaccine in a clinical drug trialomay have a late stage HIV infectionomay be infected with HIV 2 oor this may have been an erroroThis scenario would require the person to be retested at a later time. 4th generation combination immunoassay, now the gold standard test to screen for and diagnose HIV infection is the
This test is designed to detect antibodies to HIV and to detect the presence of the P24 antigen.Remember this is part of the HIV’s viral proteins. The P24 antigen can be detected as early as ten days post-infection.The combo HIV Ab/Ag test was designed to detect HIV infection early, to diagnose acute HIV infections, and to minimize the window period associated with the 3rd generation immunoassay. If the result is negative and the person is unlikely to have an acute HIV infection, then the person is negativeIf the result is positive, then an HIV-1/HIV-2 antibody differentiation immunoassay should be completedIf the test is positive and the HIV-1/HIV-2 antibody differentiation immunoassay is negative and indeterminate, then an HIV viral load should be performed to clarify the diagnosis*Condensed version of HIV tests*HIV EIA (3rdgeneration immunoassay)-it is the first test to be completed on the serum.If the EIA is negative, then the western blot is NOT completed & the person is considered to be HIV negative.If the EIA comes back positive & only if this test is positive, a western blot will be completed by the laboratory to confirm the EIA results.If the EIA is positive, & the western blot is negative, then the individual is HIV negative.