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Evaluating the utility of a two-assay serological algorithm for hepatitis C screening in a low prevalence population
Kai J Rogers1, Tracy S Halvorson1, Matthew D Krasowski1
1Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.
Introduction:
Screening for hepatitis C virus (HCV) is performed by testing for anti-HCV antibodies, which may yield false-positive results leading to additional testing and other downstream consequences for the patient. We report our experience in a low prevalence population (<0.05%) using a two-assay algorithm aimed at testing specimens with borderline or weak positive anti-HCV reactivity in the screening assay by a second anti-HCV assay prior to confirming positive anti-HCV results with RT-PCR.
Materials And Methods:
Retrospective analysis of 58,908 plasma samples was obtained over a 5-year period. Samples were initially tested using the Elecsys Anti-HCV II assay (Roche Diagnostics), with borderline or weakly positive results (defined in our algorithm as a Roche cutoff index of 0.9-19.99) reflexively analyzed using the Architect Anti-HCV assay (Abbott Diagnostics). The Abbott anti-HCV results dictated the final anti-HCV interpretation for reflexed samples.
Results:
Our testing algorithm resulted in 180 samples requiring second-line testing, with final anti-HCV results interpreted as 9% positive, 87% negative, and 4% indeterminate. The positive predictive value (PPV) of a weakly positive Roche result was 12%, which was significantly lower than the PPV using our two-assay approach (65%).
Conclusions:
The incorporation of a two-assay serological testing algorithm in a low prevalence population provides a cost-effective method of improving the PPV of HCV screening in specimens with borderline or weakly positive anti-HCV results.
