Study Results Recommend Ongoing, but Updated, HIV-1/HIV-2 Differentiation Testing

March 20, 2020

Between 2010 and 2017, there were 327,700 new HIV infections in the United States. Of these, HIV-2 infections accounted for less than 0.03% of the total. It is important to differentiate which HIV strain an individual is infected with because HIV-2 is intrinsically resistant to nonnucleoside reverse-transcriptase inhibitors, which are typically used to treat HIV-1 infections.

Between 2010 and 2017, there were 327,700 new HIV infections in the United States. Of these, HIV-2 infections accounted for less than 0.03% of the total. HIV-2 infections remain rare in the United States. They are more typically found in countries where HIV-2 infection is endemic, such as West Africa.

Using data for 2010 through 2017 from the CDC’s National HIV Surveillance System (NHSS), a group of investigators looked at trends stemming from use of the agency’s recommended HIV-1/HIV-2 differentiation test for results reported through December 2018. This test should be used in conjunction with a laboratory-based algorithm to confirm infection with the virus.

According to this recent research, which appeared in the CDC’s Morbidity and Mortality Weekly Report, “Since 2014, the recommended laboratory testing algorithm for diagnosing [HIV] infection has included a supplemental HIV-1/HIV-2 differentiation test to confirm infection type on the basis of the presence of type-specific antibodies.” The report also states that it is important to differentiate which HIV strain an individual is infected with because HIV-2 is “intrinsically resistant” to nonnucleoside reverse-transcriptase inhibitors, which are typically used to treat HIV-1 infections, and HIV-1 and HIV-2 differ in their epidemiology and clinical management.

Between 2010 and 2017, for individuals at least 13 years of age, there was a yearly increase of 21.2% (95% CI, 21.0%-21.4%) among NHSS-reported test results that included HIV-1/HIV-2 differentiation details. Associated with this is a rise in both confirmed (12.0% [95% CI, 2.8%-22.1%]) and probable (11.4% [95% CI, 1.4%-22.3%]) HIV-2 infections. In addition, from 2014—which is when the CDC began recommending the use of differentiation testing—to 2017, there was an approximate 6.4% (95% CI, 6.2%-6.9%) yearly increase in HIV-1/HIV-2 test results.

The differentiation tests have been shown to produce false-positive results, and these did increase 18.8% (95% CI, 13.3%-24.5%) each year in relation to overall HIV diagnoses. However, when considering NHSS reports that included HIV-1/HIV-2 differentiation test results, these numbers actually decreased 6.2% (95% CI, —10.7% to –1.5%) overall. The authors determined that HIV antibody cross-reactivity is to blame and suggest additional testing in these instances.

“Despite increasing use of the HIV-1/HIV-2 differentiation test, few HIV-2 infections are diagnosed in the United States. CDC continues to recommend that laboratories follow the laboratory-based algorithm with the HIV-1/HIV-2 differentiation test as the second step. Use of an HIV-1 [nucleic acid test] in the algorithm would likely distinguish type of HIV infection for the majority of diagnoses in the United States,” the authors conclude and recommend.

Reference

Peruski AH, Wesolowski LG, Delaney KP, et al. Trends in HIV-2 diagnoses and use of the HIV-1/HIV-2 differentiation test — United States, 2010—2017. MMWR Morb Mortal Wkly Rep. 2020;24;69(3):63-66. doi: 10.15585/mmwr.mm6903a2.