Performance Evaluation of the Elecsys HCV Duo Immunoassay in the Public Healthcare Setting in Cape Town, South Africa

Abstract

Improved HCV diagnosis and linkage to care is crucial to achieve WHO 2030 elimination targets. Simplification of diagnostics remains key. We evaluated the performance of Elecsys HCV Duo antigen/antibody immunoassay in patients using public healthcare in Cape Town, South Africa. 253 HCV seropositive and 214 seronegative samples were tested, and results correlated with standard-of-care (SOC) serology, HCV RNA, viral genotype, patient demographics, and disease markers. Thirteen patients on antiviral therapy were also evaluated. Elecsys HCV Duo antibody was equivalent to SOC serology, while antigen had 100% negative percent agreement in non-viraemic samples. One incident infection with viral load (VL) of 54,000 IU/mL was antigen positive/antibody negative. Overall, antigen detection was 63.2% in RNA-positive samples. VL strongly predicted reactivity, with antigen positive rates of 17.5% (< 5 log IU/mL), 75.8% (5–6 log IU/mL), 89.4% (6–7 log IU/mL), and 100% (> 7 log IU/mL). Detection in genotype-1 infections was significantly better, at 69.6% (95% CI 59.5–79.7) than non-genotype-1 at 43.2% (95% CI 28.7–57.7). In treated patients, antigen mirrored RNA clearance but was only reliable if positive at baseline. Elecsys HCV Duo detected active infection in 63% of viraemic patients, 70% with genotype 1. In our cohort, 49% of new patients would require VL testing.