Performance of a Dual Human Immunodeficiency Virus/Syphilis Rapid Test Compared With Conventional Serological Testing for Syphilis and Human Immunodeficiency Virus in a Laboratory Setting: Results From the Zimbabwe STI Etiology Study

Background: Dual human immunodeficiency virus (HIV)/syphilis rapid, point-of-care testing may enhance syphilis screening among high-risk populations, increase case finding, reduce time to treatment, and prevent complications. We assessed the laboratory-based performance of a rapid dual HIV/syphilis test using serum collected from patients enrolled in the Zimbabwe Sexually Transmitted Infections (STI) Etiology study. Methods: Blood specimens were collected from patients presenting with STI syndromes in 6, predominantly urban STI clinics in different regions of Zimbabwe. All specimens were tested at a central research laboratory using the Standard Diagnostics Bioline HIV/Syphilis Duo test. The treponemal syphilis component of the dual rapid test was compared with the Treponema pallidum hemagglutination assay (TPHA) as a gold standard comparator, both alone or in combination with a nontreponemal test, the rapid plasma reagin test. The HIV component of the dual test was compared with a combination of HIV rapid tests conducted at the research laboratory following the Zimbabwe national HIV testing algorithm. Results: Of 600 men and women enrolled in the study, 436 consented to serological syphilis and HIV testing and had specimens successfully tested by all assays. The treponemal component of the dual test had a sensitivity of 66.2% (95% confidence interval [CI], 55.2%–77.2%) and a specificity of 96.4% (95% CI, 94.5%–98.3%) when compared with TPHA; the sensitivity increased to 91.7% (95% CI, 82.6%–99.9%) when both TPHA and rapid plasma reagin were positive. The HIV component of the dual test had a sensitivity of 99.4% (95% CI, 98.4%–99.9%) and a specificity of 100% (95% CI, 99.9%–100%) when compared with the HIV testing algorithm. Conclusions: Laboratory performance of the SD Bioline HIV/Syphilis Duo test was high for the HIV component of the test. Sensitivity of the treponemal component was lower than reported from most laboratory-based evaluations in the literature. However, sensitivity of the test increased substantially among patients more likely to have active syphilis for which results of both standard treponemal and nontreponemal tests were positive. R apid point-of-care syphilis tests hold promise to enhance syphilis screening and initiate timely treatment among populations at highest risk for this infection and its consequences, including women in antenatal care settings where rapid tests may prove to be an important tool in the prevention of congenital syphilis. Combining syphilis and human immunodeficiency virus (HIV) testing From the *Rietmeijer Consulting, LLC, Denver, CO; †Colorado School of Public Health, University of Colorado Denver, Denver, CO; ‡Elizabeth Glazer Pediatric AIDS Foundation, Lesotho; §Centers for Disease Control and Prevention, Division of Global Health and Tuberculosis, Harare, Zimbabwe; ¶Centre for HIV and STIs, National Institute for Communicable Diseases, Johannesburg, South Africa; ||Department of Clinical Microbiology & Infectious Diseases, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; **Western Sydney Sexual Health Centre, Western Sydney Local Health District, Parramatta, New South Wales, Australia; ††Marie Bashir Institute for Infectious Diseases and Biosecurity & Westmead Clinical School, University of Sydney, Sydney, New South Wales, Australia; ‡‡Division of Infectious Diseases and Center for World Health, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA; §§Biomedical Research and Training Institute, Harare, Zimbabwe; and ¶¶University of Washington School of Medicine, Seattle, WA Acknowledgments: ZiCHIRe Study Team: Luanne Rodgers, Laboratory Scientist, Vitalis Kupara, State Registered Nurse (SRN), Mebbina Muswera, State Registered Nurse and State Registered Midwife (SRN, SRM), Sarah Vundhla, State Registered Nurse and State Registered Midwife (SRN, SRM), Shirley Tshimanga, State Registered Nurse and State Registered Midwife (SRN, SRM). This study could not have been conducted without the gracious support and collaboration of the staff and patients of the following clinics: Harare: Mbare and Budiriro Clinics, Bulawayo: Nkulumane and Khami Road Clinics, Beitbridge: Dulibadzimu Clinic, Gutu: Gutu Rural Hospital. Conflicts of Interest: None declared. Sources of Funding: The Zimbabwe STI Etiology Study was supported by funds from the President's Emergency Plan for AIDS Relief (PEPFAR) through a cooperative agreement between the U.S. Centers for Disease Control and Prevention and the University of Zimbabwe Department of Community Medicine SEAM Project under the terms of Cooperative Agreement Number IU2GGH. SD HIV/Syphilis BIOLINE Duo test kits were provided as an in-kind contribution to the study by the test manufacturer. Disclaimer: The findings and conclusions of this report are those of the authors and do not necessarily represent the official position of the funding agencies. Correspondence: Cornelis A. Rietmeijer, MD, PhD, MSPH, Rietmeijer Consulting LLC, 533 Marion Street, Denver, CO 20218. E‐mail: . Received for publication April 15, 2019, and accepted May 29, 2019. DOI: 10.1097/OLQ. Copyright © 2019 American Sexually Transmitted Diseases Association. All rights reserved. ORIGINAL STUDY 584 Sexually Transmitted Diseases • Volume 46, Number 9, September 2019 Copyright © 2019 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited. in a single rapid test device can expand syphilis testing coverage in areas where HIV testing is ubiquitous but syphilis testing lags behind.1 Furthermore, combined testing offers the potential to leverage existing HIV testing resources to enhance syphilis screening among pregnant women to achieve the ultimate goal of elimination of mother to child transmission of both diseases.2 A recently published systematic review shows that dual HIV/syphilis rapid tests have very high sensitivity and specificity for HIV and a lower but generally adequate sensitivity and specificity for syphilis.3 The systematic review also highlights a higher sensitivity for the treponemal component of dual rapid tests when they are used to test serum in a laboratory setting compared with testing finger-prick blood in a clinic setting.3 Finally, dual tests are more cost-effective than separate single rapid tests for HIV and syphilis and prevent more adverse pregnancy outcomes.4 On such assay is the SD Bioline HIV/Syphilis Duo test, a solid phase immunochromatographic assay for the qualitative detection of antibodies to all isotypes (IgG, IgM, and IgA) specific to HIV-1/2 and Treponema pallidum simultaneously in human serum, plasma, or whole blood. The syphilis component of this lateral-flow assay tests for the presence of treponemal antibodies. According to the manufacturer, test sensitivity/specificity are, respectively, 99.9% and 99.67% for the HIV component of the test and 99.67% and 99.72% for the syphilis component.5 In 2015, the SD Bioline HIV/Syphilis Duo Test (Abbott Laboratories, Lake Bluff, IL—hereafter “Bioline”) was accepted for the World Health Organization list of prequalified in vitro diagnostics.3 We evaluated the Bioline test as part of the Zimbabwe Sexually Transmitted Infections (STI) Etiology Study. METHODS The Zimbabwe STI Etiology Study, conducted in 2014 to 2016, examined the etiology of 3 common STI syndromes: vaginal discharge in women, urethral discharge in men, and genital ulcer disease in both men and women. Details of the study are available online,6 and the main outcomes of the study have been published elsewhere.7–10 An analysis of serological syphilis markers among patients in this study is published as a companion article in this issue of the Journal.11 The following methodological details are pertinent to this report. Among 600 patients with STI syndromes recruited for this study at 6 mostly urban clinics in Zimbabwe, 494 accepted optional venipuncture for syphilis testing, all but 5 of whom also accepted HIV testing. All specimens were kept refrigerated after collection and shipped in a cooler box with cooling packs by overnight courier to the study laboratory at Wilkins Hospital in Harare, where they were kept refrigerated until further processing. All syphilis and HIV tests were conducted at the study laboratory. Serum specimens were tested with the Bioline test according to the manufacturer's instructions. Additional syphilis serology included both treponemal and nontreponemal tests, the Treponema pallidum hemagglutination assay (TPHA) and rapid plasma reagin (RPR) test respectively (both SPINREACT, Girona, Spain). All TPHA test runs included positive and negative controls. Rapid plasma reagin reactive samples were subsequently titrated up to 1:32 dilution for quantitative analysis. HIV testing followed the algorithm promoted by the Zimbabwe Ministry of Health and Child Care standard national HIV testing algorithm: an initial test by First Response HIV1–2-O (Premier Medical Corporation, Daman, India); if positive, a confirmatory Alere Determine HIV1/2 test (Alere Inc. Waltham, MA); and, in case of discrepancy between these results, an INSTI HIV1/HIV2 test (bioLytical Laboratories Inc. Richmond, BC, Canada) as tie breaker. All tests were performed according to their package inserts. For this report, we compared the results of the treponemal component part of the Bioline test to TPHA as the gold standard and also to a combined TPHA/RPR outcome. We also applied our study data to 2 alternative syphilis screening algorithms: one based on a nontreponemal screening test (in our case RPR) followed, if reactive, by a treponemal (in our case TPHA) confirmatory test (also known as the “traditional” algorithm); and one based on a treponemal screening test (in our case the Bioline test) followed, if positive, by a second but different treponemal (TPHA) confirmatory test (a.k.a. the “reverse” algorithm).12 The HIV component of