Evaluation of a new West Nile virus nucleic acid test for screening of blood donations

BACKGROUND: West Nile virus (WNV) is transmitted to humans through mosquito bites and can be further transmitted to humans through transfusion or transplantation. Because most infected individuals are asymptomatic, blood donor screening is important in areas where WNV is endemic. These studies evaluated the performance of a new test for detection of WNV RNA in blood donations. STUDY DESIGN AND METHODS: Analytical performance evaluation included sensitivity, specificity, inclusivity, and correlation. A clinical specificity study was conducted at four blood donor testing laboratories in parallel with the cobas TaqScreen WNV Test (Roche Molecular Systems, Inc.). RESULTS: The 95% and 50% limit of detection for cobas WNV was 12.9 copies/mL (95% confidence interval [CI], 10.8–16.3) and 2.1 copies/mL (95% CI, 1.9–2.4) for WNV lineage 1, respectively, and 6.2 copies/mL (95% CI, 4.8–8.9) and 1.1 copies/mL (95% CI, 0.8–1.3) for WNV lineage 2, respectively. Clinical specificity was 100% in 10,823 donor samples tested individually (95% CI, 99.966%–100%) and 63,243 tested in pools of 6 (95% CI, 99.994%–100%). Samples of other members of the Japanese encephalitis virus serocomplex, including St Louis encephalitis, Japanese encephalitis, Murray Valley encephalitis, Usutu, and Kunjin viruses were detected by cobas WNV. CONCLUSION: The cobas WNV test for use on the cobas 6800/8800 System, a fully automated test system, demonstrated high sensitivity and specificity and is suitable for the detection of WNV in blood donors.