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

Objectives

Improved hepatitis C virus (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.

Methods

253 HCV seropositive and 214 seronegative samples were tested, and results correlated with standard-of-care (SOC) serology, RNA, viral genotype, patient demographics and disease markers. Thirteen patients on antiviral-therapy were also evaluated.

Results

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 of 54000 IU/mL was antigen positive/antibody negative. Overall, antigen detection was 62.2% in RNA-positive samples. Viral load strongly predicted reactivity, with antigen positive rates of 17.5% (<5 log IU/mL), 71.4% (5-6 log IU/mL), 89.4% (6-7 log IU/mL) and 100% (>7 log IU/mL). Antigen detection in genotype-1 infections was significantly better at 69.6% (95% CI 59.5-79.7) than for 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.

Conclusion

Elecsys HCV Duo detected active infection in 62% of viraemic patients and in 70% with genotype-1. In our cohort, 49% of newly diagnosed patients would require RNA testing.

Highlights

• Elecsys HCV Duo detected active infection in 63% of new HCV RNA positive patients

• Genotype-1 status and RNA >6 log IU/mL are determinants of antigen positivity

• In antiviral therapy, antigen mirrors RNA decay, and is useful if baseline positive

• 49% of new HCV patients would still require RNA test to determine viraemia