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PCR
assays
Qualitative assays
for proviral HIV-1 DNA. Although only a small fraction of peripheral
blood mononuclear cells (PBMC) from infected individuals carry proviral
HIV-1 DNA, they can usually be detected by PCR. Therefore, a diagnosis
of HIV-1 infection can be made by demonstrating the presence of
proviral DNA in PBMC. Assays for detecting proviral DNA employ the
polymerase chain reaction (PCR) to amplify conserved sequences in
the HIV-1 gag or pol gene. Experienced laboratories can achieve
100% sensitivity and specificity in PCR testing for HIV-1 DNA (37).
The sensitivity of HIV-1 DNA PCR assays in clinical practice is
only 96-99%, however (38-41). Strict
attention to guard against contamination from the carry over of
PCR products is essential to prevent false-positive results.
As with virus culture
and p24 antigen detection, sensitivity is lower in individuals with
higher CD4+ cell counts due to the lower titer of circulating infected
PBMC. DNA PCR assays for HIV-1 are used most often in the early
diagnosis of HIV-1 infection in neonates. Clinical applications
of these tests are relatively limited in adults, but occasionally
DNA PCR testing may be helpful in resolving indeterminate western
blots in high-risk individuals.
4/15/01
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