Diagnosis and monitoring of HCV infection using the cobas ® HCV test for use on the cobas ® 6800/8800 systems.

BACKGROUND AND OBJECTIVES: Accurate, sensitive, and specific tests for detection and monitoring of hepatitis C virus (HCV) RNA concentrations are essential for diagnosis and management of HCV infections. We evaluated the next-generation reverse-transcription real-time PCR test, cobas® HCV test for use with the cobas® 6800/8800 systems ("cobas HCV") by determining its analytical performance characteristics and clinical utility for the diagnosis and therapeutic monitoring of chronic HCV infections.

METHODS: The limit of detection (LOD), linearity, precision, specificity, matrix equivalence of plasma and serum, and quantitative agreement with the COBAS® AmpliPrep/COBAS® TaqMan® HCV Test version 2.0 ("CAP/CTM HCV v2") were evaluated. Clinical utility for the diagnosis of chronic HCV infection was demonstrated by testing plasma from HCV seropositive individuals and comparing results to a nucleic acid amplification test (NAAT) approved for use in the diagnosis of chronic hepatitis C. Clinical specificity was investigated by testing plasma from HCV antibody negative subjects with non-HCV related liver diseases. Utility for monitoring treatment response was defined by testing plasma collected during treatment of HCV genotypes (GT) 1, 2, and 3 and determining positive predictive value (PPV), negative predictive value (NPV) and the odds ratio (OR) for predicting cure (sustained virologic response 12 weeks after treatment cessation, "SVR12").

RESULTS: The cobas HCV test demonstrated an LOD of at least 15 IU/mL and measurable range from 15 to at least 1.0E + 08 IU/mL (1.2-8.0 log10 IU/mL) for GT 1-6, with high accuracy (≤0.16 log10 difference) and precision (standard deviation 0.04-0.14 log10 ) throughout the linear range. Paired plasma and serum samples showed highly correlated performance (R2  = 0.97). Quantification was 100% specific for HCV in analytical studies. Correlation with CAP/CTM HCV v2 was high in patient samples (mean titer difference: 0.05 log10 with a 95% CI: 0.03-0.06 log10 ). For the diagnosis of chronic HCV, positive and negative percent agreement between cobas HCV and the comparator NAAT were 98.8-100% on the cobas 6800 and 8800 systems. Clinical specificity of cobas HCV using samples from HCV antibody negative subjects with non-HCV related liver diseases was 99.6% and 100% on cobas 6800 and 8800 systems. In therapeutic monitoring and SVR12 prediction during experimental treatment for chronic HCV GT 1 infections, undetectable HCV RNA by cobas HCV at different on-treatment weeks had a PPV 76.8%-79.4%, NPV 29.9%-100%, and OR 1.64-47.52. During therapy of HCV GT 2 and GT 3, treatment week 4 and 12 results were: PPV, 84.7% and 75.3%; NPV, 47.8% and 50.0%; OR, 5.09 and 3.05.

CONCLUSIONS: The cobas HCV test is highly sensitive, specific, and accurate HCV RNA test for GT 1-6. It demonstrates excellent correlation with the FDA-approved CAP/CTM HCV v2 test. It is useful clinically for detection of active HCV infection in individuals that have had a positive anti-HCV antibody test result and in monitoring treatment response.