Performance characteristics of the Food and Drug Administration-licensed Roche Cobas TaqScreen West Nile virus assay

BACKGROUND: The cobas TaqScreen West Nile virus (WNV) test (Roche Molecular Systems) was licensed by the Food and Drug Administration (FDA) in August 2007 for detecting WNV RNA in pools of six or in individual donations (IDs). A series of studies established the performance characteristics of the assay and test system before FDA licensure. STUDY DESIGN AND METHODS: Analytic sensitivity was determined by probit analysis using multiple source materials. Clinical sensitivity was determined by testing a panel of 315 known WNV RNA-positive specimens. A large clinical specificity study was conducted by five laboratories during months when WNV activity was not expected. RESULTS: The 95 percent limit of detection for ID testing using the Lineage 1 Health Canada WNV reference standard was 40.3 copies per mL (95% individual donation, 35.1-47.8 copies per mL). Clinical sensitivity was 100 percent (95% confidence interval [CI], 98.8%-100%) for ID testing and 97.5 percent (95% CI, 95.1-98.9%) for minipool (MP) testing. Clinical specificity, when resolved to the ID, was 100 percent for both formats and was 99.986 percent at the MP level. CONCLUSION: The cobas TaqScreen WNV test performed on the cobas s 201 system is a fully automated test system with excellent clinical sensitivity and specificity that offers the benefits of automated sample preparation and a secure environment for donor testing information.