Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States.
University of New Mexico/Tricore Laboratories, Albuquerque, NM, United States.
Roche Molecular Systems, Pleasanton CA, United States.
Division of Medical Microbiology, Department of Pathology, The Johns Hopkins Hospital, Baltimore, MD 21287, United States. Electronic address: email@example.com.
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.
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").
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.
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.