The usefulness of a simultaneous immunoassay for hepatitis C virus antigen-antibody using the ELECSYS HCV Duo assay

The World Health Organization has a goal to eliminate the hepatitis C virus (HCV) by 2030. To achieve this, effective screening for HCV is essential. We evaluated the utility of the ELECSYS® HCV Duo immunoassay (Duo assay) for HCV screening.

This single-center retrospective study included 184 HCV patients from 2014 to 2017. We measured HCV antibody (Duo/Ab) and HCV core antigen (Duo/cAg) using the Duo assay in HCV RNA-positive samples obtained before DAA therapy. We compared Duo/cAg positivity rates according to host and viral factors. We also performed logistic regression analysis and decision tree analysis to identify independent factors and profiles for Duo/cAg false-negative results, respectively.

Duo/Ab positivity rates were 100%, and Duo/cAg positivity rates were 78% in all subjects. Duo/cAg positivity rates were 40.0%, 78.6%, and 92.9% at HCV RNA levels ≤4.9, 5.0-5.9, and ≥6.0 log IU/mL, respectively (p<0.0001). There were no significant differences in Duo/cAg positivity rates by gender, age, body mass index, ALT >30 U/L, and HCV genotype. In multivariate analysis, the HCV RNA level (Unit -1.0 log IU/mL, OR 5.49, CI 3.12-10.56, p<0.0001) was the only independent factor associated with Duo/cAg false-negative results. Decision tree analysis revealed that HCV RNA ≥5.7 log IU/mL was the profile associated with the lowest false-negative rate (7.4%). In contrast, HCV RNA <4.4 log IU/mL was the profile associated with the highest false-negative rate (100%).

The Duo assay identified approximately 80% of HCV carriers without HCV RNA measurement, regardless of patient background, providing substantial clinical, economic, and time-saving benefits. However, clinicians should be aware of limitations in patients with low HCV RNA levels.