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  • In this new therapeutic era nucleic acid


    In this new therapeutic era, nucleic Dp44mT amplification tests (NAATs) remain critically useful. NAATs are recommended to detect HCV RNA in blood following initial serologic diagnosis of HCV infection, to distinguish between spontaneous resolution and progression to chronic infection [7]. In treatment management, NAATs are primarily used to demonstrate therapeutic response, although some guidelines recommend using baseline HCV RNA levels as an adjunct for the duration of certain DAA regimens [3]. As we move towards eradication of HCV, laboratories performing HCV NAATs will experience increased test volumes, creating demand for high-throughput automated instrumentation that can perform HCV RNA quantification tests that are sensitive, specific, and accurate for use in the medical management HCV infection. The cobas HCV quantitative nucleic acid test (“cobas HCV”) is a fully automated assay for the detection and quantification of HCV RNA for use on the cobas® 6800/8800 systems, which are instruments designed for medium and high throughput testing (384 and 960 tests, respectively, per 8 h shift). The higher throughput of the 8800 is accomplished solely with the addition of two real-time PCR modules (6800 has two, 8800 has four); extraction hardware is identical between the two platforms. This new-generation HCV test system uses novel real-time PCR assay reagents and instrumentation (inclusive of software) compared to the last generation COBAS AmpliPrep/COBAS TaqMan HCV Test v2.0.
    Objective This study determined the performance characteristics of the cobas® HCV test for the quantification of HCV RNA in human plasma and/or serum from HCV-infected individuals and defined the clinical utility of the test for the detection of chronic HCV in seropositive individuals and prediction of SVR during therapeutic monitoring.
    Study design
    Discussion Herein we demonstrated that cobas HCV has critical performance characteristics that allow for its use as a diagnostic test for the detection of chronic hepatitis C in HCV seropositive individuals and as a tool in the management of treatment with DAAs. For example, cobas HCV’s low LOD (7–14 IU/mL depending on genotype and plasma/serum matrix) meets the level recommended by guidelines for NAATs with diagnostic utility [2,3,13]. This sensitivity was observed for HCV GT 1–6, a useful and desirable feature given Clone genotypes that were once rare (GT 4–6) are now increasingly observed as diverse populations access care for HCV, attracted by the promise of cure with DAA therapy. Other findings of our study that further support the functionality of cobas HCV as a test for the diagnosis of chronic hepatitis C include its analytical specificity, clinical specificity, and near-perfect agreement with other NAATs approved for the diagnosis of chronic hepatitis C. Quantitative HCV NAATs are used in the medical management of DAA treatment to determine baseline HCV RNA levels, to assess treatment response early (after 4 weeks of treatment), to inform the decision to discontinue treatment after treatment week 6 in individuals with unchanged or rising HCV RNA levels, to assess virologic response at the end of treatment, and to determine SVR12. The performance requirements for quantitative HCV RNA NAATs used in DAA treatment management are driven by these uses. Specifications for the upper limit of quantification of HCV NAATs are lacking in clinical guidelines. However, retrospective analysis of quantitative HCV results in the DAA era (10/1/2016–1/1/2017) performed as part of quality assurance demonstrated 1.1% (28/2658) were ≥1.0E + 07 IU/mL (7.0 log10 IU/mL) and none were greater than ≥1.0E + 08 IU/mL (8.0 log10 IU/mL; A.V., unpublished data), suggesting that an upper limit of quantification of 1.0E + 08 IU/mL (8.0 log10 IU/mL) is a useful and appropriate performance characteristic from a practical, clinical perspective. For the determination of therapeutic response at end of treatment and SVR12, guidelines have advocated the use of HCV RNA NAATs with a limit of detection/lower limit of quantification ≤15 IU/mL [3]. For the early identification of individuals who are not responding to treatment, NAATs for HCV RNA quantification should have adequate precision within the measuring range such that a 10-fold increase in HCV RNA between treatment weeks 4 and 6 can be reliably determined allowing for discontinuation of therapy as recommended by current guidelines [2].