HIV Testing

HIV is a complex retrovirus of the lentivirus subgroup. It contains two copies of singlestranded viral RNA (1:305). The HIV genome contains structural genes that encode the proteins of the whole virus particle as well as replicative enzymes. The retrovirus also contains at least eight additional regulatory and accessory genes that regulate its life cycle (1:306).

Within about 4 to 6 weeks of initial HIV infection there is a period of viremia without detectable antibodies (1:306). During this phase, high levels of plasma antigen can be cultured from plasma and peripheral blood mononuclear cells (PBMC). As the infection progresses, however, the viremia declines to a low level (1:306).

The development of antibody normally occurs 6 to 8 weeks after infection (5:2861). The process begins with an IgM response which progresses to an IgG response (1:306).

The different HIV tests used in clinical laboratories and research protocols include antibody tests, direct antigen detection assays, and other tests (1:308).

The detection of HIV antibody remains the most efficient and commonly used method to prove HIV exposure and screen blood products (1:308). A test for HIV antibodies is considere

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essible (1:312). There is only one restricted FDA licensed LA assay available in the United States (1:312). This LA assay test uses latex beads, coated with recombinant antigen, admixed with a small amount of whole blood serum and rotated on a card (1:312). The suspension is evaluated by eye in bright light after 3 minutes for agglutination relative to a negative control (1:312). Application of the LA assay in US populations with a low and high prevalence of HIV infection has shown that the test has a sensitivity from 92% to 99% and a specificity of 99% (1:312). One report, however, noted a 20% interobserver variation, related to the difficulty in assessing weak agglutination reactions and indicating a high possibility of misreadings (1:312). Therefore, specimens reactive by LA assay should definitely undergo further confirmatory testing (1:312). The most commonly used confirmatory test for the presence of HIVspecific antibodies is the Western blot test (2:S24). Currently, there is one FDA licensed commercial WB kit available (1:313). Compared with ELISA, the WB is more expensive, time consuming, and requires more technical expertise due the subjective nature of its interpretation (1:313). While the overall sensitivit
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Approximate Word count = 1835
Approximate Pages = 7 (250 words per page)

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