Downloaded from http://journals.lww.com/stdjournal by BhDMf5ePHKbH4TTImqenVJua3JJgqHHloZDaxzhQKVd5QMkOH2LaBx2LBxpScY8u on 06/16/2020 Rapid Testing Algorithm Performance in a Low-Prevalence Environment Eugene G. Martin, PhD,* Julia Cornett, MD,†‡ Debbie Y. Mohammed, DrPH,§ and Gratian Salaru, MD¶ Background: The performance of a statewide HIV rapid test algorithm (RTA) in a low-prevalence setting (0.71%) was examined for 3 years. Methods: An initial rapid screening by HIV-1/2 Ag/Ab Combo test (RT#1) with Ab verification using a second, different rapid test (RT#2) was conducted. Clinic referral was immediate for antigen-only–positive screens. Antibody- positive screens were confirmed by RT#2. Specimens were collected fol- lowing discordant RTA results (initially Ab-POS by RT#1, but negative on RT#2) and tested in accordance with the current Centers for Disease Control and Prevention/Association of Public Health Laboratories–based HIV diag- nostic algorithm supplemented by a quantitative viral load whenever possible. Results: Of 310,785 tests performed, 2400 preliminary positive screens were identified; 2191 (91.8%) confirmed by RT#2. Of 13 Determine Combo AG-POS results identified, only 1 confirmed positive. Of the remaining 196 discordant results, 182 (92.9%) were uninfected, including 13 with AG-POS/AB-POS results. Of 14 true positives (7.1%) identified after dis- cordant RTA results, the average quantitative HIV-1 viral load was 277,385 copies/mL, but 5 (35.7%) of 14 had viral loads <1000 copies/mL. Among the 2191 “presumptive positive” by RTA, 3 false-positive (FP) RTAs were reported (both rapid tests having positive results, while the HIV-1/2 Ag/Ab assay and quantitative HIV-1 viral load showed negative results). Conclusions: The RTA was effective in predicting true-positive HIV test results and facilitating linkage to care. Discordant results were infrequent. Fingerstick DC Ag detection identified a single early infection. Many dis- cordant cases that were subsequently positive were associated with viral loads <1000 copies/mL. A mong marginalized groups, stigma and poverty often interfere with acceptance of laboratory-based HIV testing in traditional health care settings. 1 This has led to innovative approaches using simple rapid testing algorithms (RTAs) to achieve outreach, iden- tification, and linkage to medical care for persons living with HIV (PLWHs). Many initiatives rely on rapid HIV diagnostic tests (RDTs) administered in community-based settings by operators not formally trained in laboratory technology. Conducted with adequate quality assurance, and clearly de- fined protocols and procedures, 2 RDTs can be performed with great sensitivity and specificity. Nonetheless, they are susceptible to operator errors including pipetting, timing, and reading-related issues. Adding a second “confirmatory” rapid test (RT#2) to an ini- tial positive (RT#1) has advantages compared with the delayed con- firmation associated with standard laboratory testing. 3 An RTA can presumptively and reliably confirm an initial positive RT result in a high-prevalence setting. Although the World Health Organization's protocols allows for a third, tie-breaker rapid test to determine an HIV diagnosis in high-prevalence, resource-limited settings, 4 in high-resource communities, an HIV diagnosis hinges upon subse- quent laboratory-based confirmation. In settings of very low HIV prevalence, the predictive value of a single positive rapid test result can be potentially improved by a strategy that uses a second, different manufacturer's rapid test to achieve independent (orthogonal) verification of the initial prelim- inary positive result. In the United States, discordant RTA results are commonly resolved by use of the Centers for Disease Control and Prevention (CDC) laboratory algorithm, 5 which recommends an instrumented antigen/antibody HIV combination screening immunoassay and, if reactive, followed by an HIV-1/HIV-2 antibody differentiation im- munoassay. Instrumented antigen/antibody tests are preferred over a rapid combination (Determine Combo [DC] Ag/Ab) test, as they are more sensitive to the presence of p24 antigen, an early marker of an acute HIV infection. 6,7 When the differentiation assay is interpreted as negative or indeterminate for HIV-1, a reflex to a qualitative HIV-1 nucleic acid test is recommended. The New Jersey (NJ) RTA provides verification of initial, positive HIV1/2 antibody screening results, using an orthogonal rapid test (RT#2) as well as an expedited pathway into care for those identified as possibly very infectious (free p24 Ag ONLY). By modi- fying the RTA for use with a rapid HIV1/2 Ag/Ab test, we hoped to increase the identification of early infections. During a 3-year period (2015–2018), we sought to evaluate the performance of the algorithm and the utility of the antigen biomarker in a low-prevalence setting. We were interested in determining how often concordant rapid test results were confirmed as true infection, how often a discordant result portended a false-positive (FP) screen result, and how often a free p24 antigen-positive result was observed and subsequently confirmed. MATERIALS AND METHODS Clinical faculty from Rutgers University– Robert Wood Johnson Medical School (RWJMS) (New Brunswick, NJ) support a statewide rapid screening network consisting of 136 sites (92 oper- ated under RWJMS Clinical Laboratory Improvement Amendments [CLIA] waiver), whereas an additional 44 sites operate under CLIA waivers held by other entities. All sites use the NJ HIV quality as- surance framework (http://www.njhiv1.org) and procedures pro- vided by RWJMS. Rapid HIV test shipments are validated centrally using com- mercially available HIV performance panels and distributed from a single location to testing facilities throughout New Jersey. From the *Department of Pathology and Laboratory Medicine, Rutgers University – Robert Wood Johnson Medical School, Somerset; †Di- vision of Infectious Diseases, Department of Medicine, and ‡De- partment of Laboratory Pathology and Laboratory Medicine, Rutgers University – Robert Wood Johnson Medical School, New Brunswick; §Department of Nursing, William Paterson University, Wayne; and ¶Rutgers University – Robert Wood Johnson Medical School, New Brunswick, NJ Conflict of Interest and Sources of Funding: The authors report no con- flict of interest. This work received funding support from the State of New Jersey Department of Health, Division of HIV, STD & TB Services: AIDS19CTN025. Correspondence: Eugene G. Martin, PhD, Department of Pathology and Laboratory Medicine, 1 World's Fair Drive, Rm 2211, Somerset, NJ 08873. E‐mail: martineu@rwjms.rutgers.edu. Received for publication October 24, 2019, and accepted December 11, 2019. DOI: 10.1097/OLQ.0000000000001138 Copyright © 2020 American Sexually Transmitted Diseases Association. All rights reserved. ORIGINAL STUDY Sexually Transmitted Diseases • Volume 47, Number 5S, May 2020 S35 Copyright © 2020 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.