An opt-out approach to testing for HIV in the emergency department (ED) is feasible using a fourth-generation antigen/antibody laboratory test, finds a study recently published in Annals of Emergency Medicine and funded by the Centers for Disease Control and Prevention (CDC).

“The main implication from this study is that fourth-generation HIV testing, which identifies both HIV antigen and antibody, allows for earlier diagnosis of HIV,” explains Kara I. Geren, MD, MPH, lead author of the paper. “Patients present to the ED with symptoms of acute HIV infection but, in the past, due to imperfect technology, these infections were missed. Now patients, both symptomatic and asymptomatic, can be diagnosed with HIV.”

The study involved patients at the Maricopa Medical Center ED in Phoenix who had blood drawn and did not opt out of HIV testing. Those with known HIV or AIDS, altered mental states, or who lived in psychiatric or correctional facilities were not included in the study.

The hospital laboratory used Abbott Laboratories’ Architect HIV Ag/Ab Combo Test on patients’ whole blood samples. Any preliminary positive result automatically triggered testing with Bio-Rad Laboratories’ third-generation Multispot HIV-1/HIV-2 Rapid Test. When the study started, the lab performed confirmatory testing with Cambridge Biotech’s HIV-1 Western blot qualitative antibody test and Abbott Laboratories’ RealTime HIV-1 Assay. However, in anticipation of new recommendations from CDC, 9 months into the study, the investigators stopped using Western blot.

Just under 28,000 HIV screenings were performed for 22,468 patients between July 11, 2011, and Jan. 5, 2014. Overall, there were 105 preliminary positive results and 78 confirmed, newly diagnosed HIV cases. Of the 27 false positives, three had nonreactive third-generation test results, negative or indeterminate Western blot (in the period of time this test was used), and had no detectable viral load. The remaining 24 had non-reactive third-generation results and no detectable viral load. Of the 78 newly confirmed cases, 18 were acute infections that would have gone undetected by standard screening.

“Identification and treatment of patients with acute HIV infections decreases the transmission of HIV and improves long-term morbidity and mortality,” Geren says. “Given nearly 25% of patients with a new HIV diagnosis in this study are acute infections, this translates into fewer HIV infections and more patients with HIV in care.”