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TABLE 2-4:

Tests for HIV-1 (continued)
Assay Sensitivity Comments
DNA PCR
assay		 >99% Qualitative DNA PCR is used to detect cell-associated
proviral DNA, including HIV reservoirs in peripheral CD4
cells in patients responding to HAART with a sensitivity
of about 5 copies/106 cells (J Virol Methods 2005;124:
157). This is not considered sufficiently accurate for
diagnosis without confirmation and is not FDA
approved (Ann Intern Med 1996;124:803), although it is
occasionally used when other tests are disputed or
serology is indeterminate.
HIV RNA PCR 95% to
98%		 False positive tests in 2% to 9%, usually at low titer
(<10,000 c/mL). Sensitivity depends on viral load,
threshold of assay, and status of antiretroviral therapy.
Sensitivity approaches 100% with acute HIV infection;
specificity is 97%, but nearly 100% with viral load
>10,000 c/mL.
p24 antigen 30% to
90%		 Sometimes used as an alternative to HIV RNA test to
detect acute HIV infection due to reduced cost.
Specificity is 100%, but sensitivity is about 90% – less
than quantitative HIV RNA tests (Ann Intern Med
2001;134:25). Another use is as a lower-cost
alternative to VL testing in resource-limited countries
(J Clin Micro 2005;43:506).

 

Viral Detection

Other methods to establish HIV infection include techniques to detect DNA (HIV-1 DNA PCR) or RNA (HIV-1 RNA) by bDNA or RT-PCR (Table 2-4, pg 17). HIV-1 DNA PCR is the most sensitive and can detect 1 to 10 copies/mL of HIV proviral DNA, but the reagents are not well standardized nor FDA-approved. None of these tests is considered to be more accurate than routine serology, but some may be useful in patients with confusing serologic test results, and for HIV detection when routine serologic tests are likely to be misleading, as in patients with agammaglobuline mia, acute retroviral infection, neonatal HIV infection, and patients in the window period following viral exposure. In most cases, con firmation of positive serology is accomplished simply by repeat serology or viral load testing.

Quantitative Plasma HIV RNA (Viral Load)

TECHNIQUES (see Table 2-5, pg 23)

  • HIV RNA PCR: Amplicor HIV-1 Monitor Test version 1.5, Roche; 800- 526- 1247.
  • Branched chain DNA or bDNA: Versant HIV-1 RNA 3.0 Assay, Seimans Diagnostics (formerly Bayer);800-434-2447.
  • Nucleic acid sequence-based amplification (NABSA): NucliSens HIV- 1 QT (bioMérieux), 800-682-2666.
2007 © John G. Bartlett, M.D. All rights reserved.18

Chapter 2: Laboratory Tests

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