FALSE-POSITIVE RESULTS ARE POSSIBLE WITH HIV-1 RNA ASSAY

Reuters 13 Nov. '00

Westport, CT -- The use of an HIV-1 RNA assay as a diagnostic tool in patients suspected of having acute retroviral syndrome may lead to a significant number of false-positive results in a large patient population, according to Texas-based researchers.

Dr Daniel More and colleagues from Wilford Hall Medical Center, Lackland AFB, point out that although the reverse transcription polymerase chain reaction (RT-PCR) viral load assay is a sensitive measurement for HIV-1 viral load, the false-positive and false-negative rates range from 1.9% to 3.0%, respectively.

In the October issue of the Southern Medical Journal, the authors report what they believe to be the first case of a young, sexually active woman with symptoms suggestive of acute retroviral syndrome who had a false-positive HIV-1 RNA assay result. They also discuss the diagnostic issues that arise in what they say "is likely to become a common clinical scenario."

The patient presented with frontal headaches, cervical lymphadenopathy, macular rash, fever, night sweats, and oral aphthous ulcers. "Liver function tests, serum chemistry values, urinalysis, thyroid stimulating hormone, and complete blood count were within normal limits," they write. Throat culture for beta-hemolytic streptococci was negative, as were results of the monospot test and serology test for Epstein-Barr virus.

According to the team, the 23-year-old women was HIV-1 negative according to the results of enzyme-linked immunosorbent assay and Western blot serology tests. An HIV-1 RT-PCR assay, however, showed a viral load of 623 copies/mL, "though p24, gp120, and gp160 antigens were not present." The assay was repeated with similar results. However, treatment with highly active antiretroviral therapy was postponed until further evaluation.

Because the patient continued to experience symptoms suggestive of acute retroviral syndrome, the researchers repeated the HIV-1 RT-PCR and p24 antigen test 2 weeks later. Results of these tests were negative, they report, "making it increasing unlikely that our patient had primary HIV- 1 infection." The results of ELISA and Western Blot tests repeated 4 months after the initial result were still negative.

"Despite the occurrence of false-positive results," Dr More and colleagues point out that "the HIV-1 RT-PCR assay offers the earliest laboratory evidence of [the] diagnosis [of acute retroviral syndrome.]" However, they add, "our case ... emphasizes the need to determine whether the HIV-1 viral load results are in a range that is typically seen in HIV-1 seroconversion." If the viral load is lower than excepted in primary infection, "the clinician must reassess the patient's risk factors for HIV-1 and should consider repeating the HIV-1 RT-PCR assay with p24 antigen testing."

South Med J. 2000;93:1004-1006.