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Nucleic-Acid Amplification Testing Might Improve Detection of Acute Infection

Adding nucleic-acid testing to standard antibody testing improved the detection of acute HIV infection in North Carolina — and was cost-effective.

HIV diagnosis during acute infection is extremely challenging. Unfortunately, very early infection appears to be a time of markedly increased infectiousness. These researchers evaluated whether the identification of acute infection in North Carolina could be improved by adding nucleic-acid amplification testing to standard antibody testing at 110 state-funded testing and counseling sites.

During a 12-month period, 109,250 individuals at these sites were tested for HIV antibody using standard enzyme immunoassay and Western blot; 583 subjects were found to have established infection, including 107 with probable recent infection (according to results from a detuned ELISA). Taking advantage of a centralized HIV-testing laboratory, the study group reevaluated all of the HIV-antibody–negative and indeterminate samples using an automated specimen-pooling technique that produced a single sample containing blood from 90 different patients. These "master pool" samples were tested for HIV RNA using the NucliSens HIV-1 QL assay, which yielded a positive result if any specimen in the pool contained at least 6750 copies of HIV RNA/mL. Master pools that tested positive were broken into smaller pools and then into individual samples until the positive specimen was identified.

Of the people who had negative or indeterminate results on standard antibody testing, 25 had positive results on nucleic-acid testing. Two were later determined to have false-positive results, and the other 23 were confirmed to have acute infection. Of these 23, 20 started antiretroviral therapy. Risk-reduction counseling and HIV testing were offered to sexual partners, leading to the identification of another 5 HIV-infected individuals. Adding nucleic-acid testing to the standard protocol cost US$3.63 per tested sample and $17,515 per HIV case identified. The specificity of nucleic-acid testing with standard antibody testing was >0.999, and the positive predictive value was 0.997.

Comment: This sample-pooling strategy allowed researchers to test large numbers of individual specimens with a relatively modest investment of resources. In addition to improving epidemiologic surveillance of HIV infection in North Carolina, this approach also brought individuals with acute infection into HIV care quickly. Moreover, notifying individuals of their test results and providing prevention counseling almost certainly reduced the number of secondary transmissions from these cases. Having all HIV testing for state-funded sites done in a single laboratory made this testing approach accessible for the entire state. Critical to its success was the commitment of sufficient personnel and resources to permit timely testing, rapid notification, and contact tracing. More widespread adoption of this method beyond North Carolina might significantly enhance the diagnosis and management of acute HIV infection on a larger scale.

— Charles B. Hicks, MD

Published in AIDS Clinical Care May 11, 2005

Citation(s):

Pilcher CD et al. Detection of acute infections during HIV testing in North Carolina. N Engl J Med 2005 May 5; 352:1873-83.

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