B-222 HCV Antigen Assay Demonstrates High Sensitivity and Specificity for Hepatitis C Detection

Abstract

Hepatitis C virus (HCV) is a blood-borne retrovirus that has caused significant morbidity and mortality globally. The CDC estimates that there are ∼69,000 new acute infections and 11,000 deaths per year in the US. Direct-acting antiretroviral treatments effectively cure patients HCV and are being used administered and prescribed in some ED settings to reduce HCV burden. However, such an approach requires rapid confirmation of HCV infection. The current CDC algorithm relies on HCV positive antibody (Ab) testing before a reflex to confirmatory nucleic acid amplification testing (NAAT). This approach yields many positive antibody results that do not confirm viremia, and has significant turnaround time, delaying linkage to care. While not currently included in CDC algorithms, rapid HCV antigen (Ag) testing may reduce the bottleneck of molecular testing, but assays must be sufficiently sensitive and specific. We sought to assess the clinical performance of two commercially available HCV Ab and Ag assays. We tested 1,100 remnant clinical serum samples in patients with physician ordered HCV testing. All samples were also tested with the Abbott NXT anti-HCV, Abbott NXT HCV Ag assay (RUO), the Abbott anti-HCV II assay, the Roche DUO anti-HCV Ab and Ag assay and HCV NAAT was performed to confirm viremia. Concordance, sensitivity (sens), and specificity (spec) were calculated relative to NAAT results. Results are reported with 95% confidence intervals. Chart review was performed for all specimens to assess demographics and risk factors with discordant results. There were 214 (19.5%) patients with positive HCV NAAT. Of HCV+ patients, 134 (62.6%) were male vs. 430 (48.0%) in the HCV- group. The HCV+ patients had a higher incidence of IV drug use (68.7% vs 28.7%) and homelessness (43% vs. 15.8%). The sensitivity and specificity for each assay relative to NAAT was: Abbott NXT Ab: Sens= 100% (98.3-100), spec= 48.9 (45.6-52.3). Abbott Ag: Sens= 96.7% (93.4-98.7), spec= 99.1% (98.2-99.6), HCV Duo Ab: sens= 99.6% (97.5-100), spec=50.2% (46.9-53.6). HCV Duo Ag sens= 73.8% (67.4-79.6) spec=99.9% (99.4-100). Abbott anti-HCV II: sens=99.6% (97.5-100), spec= 52.2% (48.9-55.5). The overall concordance between the Roche Ag and Abbott Ag assays was 0.82 (0.77-0.87) and for the Roche Ab and Abbott NXT Ab was 0.96 (0.94-0.98). Antigen testing may be a rapid and accurate method for confirming HCV infection in antibody positive patients. Implementing this approach could shorten time to diagnosis and significantly reduce the costs associated with confirmatory NAAT testing. In this cohort, the Abbott Ag assay had higher sensitivity and similar specificity for HCV.