BACKGROUND: Fourth-generation HIV assays detect both antigen and antibody, facilitating detection of acute/early HIV infection. The Bio-Rad GS HIV Combo Ag/Ab assay (Bio-Rad Combo) is an enzyme immunoassay that simultaneously detects HIV p24 antigen and antibodies to HIV-1 and HIV-2 in serum or plasma. OBJECTIVE: To evaluate the performance of the Bio-Rad Combo assay for detection of HIV infection in adults from Southern Africa. STUDY DESIGN: Samples were obtained from adults in Soweto and Vulindlela, South Africa and Dar es Salaam, Tanzania (300 HIV-positive samples; 300 HIV-negative samples; 12 samples from individuals previously classified as having acute/early HIV infection). The samples were tested with the Bio-Rad Combo assay. Additional testing was performed to characterize the 12 acute/early samples. RESULTS: All 300 HIV-positive samples were reactive using the Bio-Rad Combo assay; false positive test results were obtained for 10 (3.3%) of the HIV-negative samples (sensitivity: 100%, 95% confidence interval [CI]: 98.8-100%); specificity: 96.7%, 95% CI: 94.0-98.4%). The assay detected 10 of the 12 infections classified as acute/early. The two infections that were not detected had viral loads<400 copies/mL; one of those samples contained antiretroviral drugs consistent with antiretroviral therapy. CONCLUSIONS: The Bio-Rad Combo assay correctly classified the majority of study specimens. The specificity reported here may be higher than that seen in other settings, since HIV-negative samples were pre-screened using a different fourth-generation test. The assay also had high sensitivity for detection of acute/early infection. False-negative test results may be obtained in individuals who are virally suppressed.

Center for World Health David Geffen School of Medicine and UCLA Health Los Angeles CA USA

Department of Pathology Johns Hopkins University School of Medicine Baltimore MD USA

Department of Probability and Statistics Faculty of Mathematics and Physics Charles University Prague Czech Republic

Department of Psychiatry and Behavioral Sciences The Medical University of South Carolina Charleston SC USA

DST NRF Centre of Excellence in Human Development Universities of the Witwatersrand and KwaZulu Natal South Africa; Human Sciences Research Council Durban South Africa

Muhimbili University of Health and Allied Sciences Muhimbili University Teaching Hospital Dar es Salaam Tanzania

Perinatal HIV Research Unit Chris Hani Baragwanath Hospital University of the Witwatersrand Johannesburg South Africa; South African Medical Research Council Cape Town South Africa

Program in Global Health University of California at Los Angeles Los Angeles CA USA

Vaccine and Infectious Disease Division Fred Hutchinson Cancer Research Center Seattle WA USA; Department of Global Health University of Washington Seattle WA USA

See more in PubMed

Cornett JK, Kirn TJ. Laboratory diagnosis of HIV in adults: a review of current methods. Clin Infect Dis. 2013;57:712–8. PubMed

US Food and Drug Administration. [accessed 19.11.13];Complete list of donor screening assays for infectious agents and HIV diagnostics assays. Available at: http://www.fda.gov/BiologicsBloodVaccines/BloodBloodProducts/ApprovedProducts/LicensedProductsBLAs/BloodDonorScreening/InfectiousDisease/ucm080466.htm.

Bentsen C, McLaughlin L, Mitchell E, Ferrera C, Liska S, Myers R, et al. Performance evaluation of the Bio-Rad Laboratories GS HIV Combo Ag/Ab EIA, a 4th generation HIV assay for the simultaneous detection of HIV p24 antigen and antibodies to HIV-1 (groups M and O) and HIV-2 in human serum or plasma. J Clin Virol. 2011;52(Suppl 1):S57–61. PubMed

Bio-Rad Laboratories. Product package insert. [accessed 23.12.13];GS Combo Ag/Ab EIA. Available at: http://www.fda.gov/downloads/BiologicsBloodVaccines/BloodBloodProducts/ApprovedProducts/PremarketApprovalsPMAs/UCM266211.pdf.

Malia J, Manak M, Shutt A, Bentsen C, Shriver K, Peel S. Evaluation of the fourth generation GS HIV Combo Ag/Ab EIA on low and high prevalence populations, abstr THPE059. XIX international AIDS conference; 2012.

Mitchell EO, Stewart G, Bajzik O, Ferret M, Bentsen C, Shriver MK. Performance comparison of the 4th generation Bio-Rad Laboratories GS HIV Combo Ag/Ab EIA on the EVOLIS automated system versus Abbott ARCHITECT HIV Ag/Ab Combo, Ortho Anti-HIV 1+2 EIA on Vitros ECi and Siemens HIV-1/O/2 enhanced on Advia Centaur. J Clin Virol. 2013;58(Suppl 1):e79–84. PubMed

Nasrullah M, Wesolowski LG, Meyer WA, 3rd, Owen SM, Masciotra S, Vorwald C, et al. Performance of a fourth-generation HIV screening assay and an alternative HIV diagnostic testing algorithm. AIDS. 2013;27:731–7. PubMed PMC

Eller LA, Manak M, Malia J, de Souza M, Shikuku K, Lueer C, et al. Reduction of HIV window period by 4th gen HIV combination tests, abstr O-142. 20th conference on retroviruses and opportunistic infections; 2013.

Hemelaar J, Gouws E, Ghys PD, Osmanov S. Global trends in molecular epidemiology of HIV-1 during 2000–2007. AIDS. 2011;25:679–89. PubMed PMC

Laeyendecker O, Piwowar-Manning E, Fiamma A, Kulich M, Donnell D, Bassuk D, et al. Estimation of HIV Incidence in a large, community-based, randomized clinical trial: NIMH Project Accept (HIV Prevention Trials Network 043) PLOS ONE. 2013;8:e68349. PubMed PMC

Coates TJ, Kulich M, Zelaya CE, Celantano DD, Chariyalertsak S, Chingono A, et al. Outcomes from NIMH Project Accept (HPTN 043): a cluster-randomized trial of community mobilization, mobile HIV testing, post-test support services, and real-time performance feedback. Lancet Glob Health. 2014 (in press) PubMed PMC

Piwowar-Manning E, Fiamma A, Laeyendecker O, Kulich M, Donnell D, Szekeres G, et al. HIV surveillance in a large, community-based study: results from the pilot study of Project Accept (HIV Prevention Trials Network 043) BMC Infect Dis. 2011;11:251. PubMed PMC

Chen I, Cummings V, Fogel JM, Marzinke MA, Clarke W, Connor MB, et al. Low-level viremia early in HIV infection. J Acquir Immune Defic Syndr. 2014 (in press) PubMed PMC

Branson BM, Owen SM, Wesolowski LG, Bennett B, Werner BG, Wroblewski KE, Pentella MA. [accessed 30.06.14];Laboratory testing for the diagnosis of HIV infections. Available at: http://www.cdc.gov/hiv/pdf/HIVtestingAlgorithmRecommendation-Final.pdf.

Centers for Disease Control and Prevention (CDC) Detection of acute HIV infection in two evaluations of a new HIV diagnostic testing algorithm – United States, 2011–2013. MMWR Morb Mortal Wkly Rep. 2013;62:489–94. PubMed PMC

Fiebig EW, Wright DJ, Rawal BD, Garrett PE, Schumacher RT, Peddada L, et al. Dynamics of HIV viremia and antibody seroconversion in plasma donors: implications for diagnosis and staging of primary HIV infection. AIDS. 2003;17:1871–9. PubMed

Ananworanich J, Fletcher JL, Pinyakorn S, van Griensven F, Vandergeeten C, Schuetz A, et al. A novel acute HIV infection staging system based on 4th generation immunoassay. Retrovirology. 2013;10:56. PubMed PMC

Swaminathan S, Hanna LE, Sundaramurthi JC, Leonard A, Angayarkanni B, Francis AC, et al. Prevalence and pattern of cross-reacting antibodies to HIV in patients with tuberculosis. AIDS Res Hum Retroviruses. 2008;24:941–6. PubMed

Lejon V, Ngoyi DM, Ilunga M, Beelaert G, Maes I, Buscher P, et al. Low specificities of HIV diagnostic tests caused by Trypanosoma brucei gambiense sleeping sickness. J Clin Microbiol. 2010;48:2836–9. PubMed PMC

Klarkowski D, O’Brien DP, Shanks L, Singh KP. Causes of false-positive HIV rapid diagnostic test results. Expert Rev Anti Infect Ther. 2014;12:49–62. PubMed

Piwowar-Manning E, Fogel JM, Laeyendecker O, Wolf S, Cummings V, Marzinke MA, et al. Failure to identify HIV-infected individuals in a clinical trial using a single HIV rapid test for screening. HIV Clin Trials. 2014;15:62–8. PubMed PMC

Marzinke MA, Clarke W, Wang L, Cummings V, Liu T-Y, Piwowar-Manning E, et al. Non-disclosure of HIV status in a clinical trial setting: antiretroviral drug screening can help distinguish between newly-diagnosed and previously-diagnosed HIV infection. Clin Infect Dis. 2014;58:117–20. PubMed PMC

Fogel JM, Wang L, Parsons TL, Ou SS, Piwowar-Manning E, Chen Y, et al. Undisclosed antiretroviral drug use in a multi-national clinical trial (HPTN 052) J Infect Dis. 2013;208:1624–8. PubMed PMC