Evaluation of various real-time RT-PCR assays for the detection and quantitation of human norovirus.

Human noroviruses (NoVs) are the most common viruses causing acute gastroenteritis in humans. Performance characteristics of two commercial quantitative NoV RT-PCR assays, the Norovirus real-time RT-PCR Kit (AnDiaTec) and the Type I and Type II kits (Generon), and the international assay as selected by the CEN/TC/WG6/TAG4 group were evaluated for the specific detection and quantitation of 59 NoV samples, including different subtypes of NoV genogroup I and II. The results showed that the method proposed by the CEN/TC/WG6/TAG4 group was 100% specific since it was able to detect all samples tested. The commercialized kits evaluated failed to detect a vast majority of NoV GI strains. Additionally the Generon kit did not succeed to detect strains from GII.3, GII.5, GII.6, GII.7, GII.8, GII.12 and GII.17. In addition, the detection limit using the most prevalent strain, NoV GII.4, was 2.5 PCRU per reaction using both commercial kits. Despite this good sensitivity for NoV GII.4 detection it is concluded that both commercial assays are not suitable for the detection and quantitation of most NoV subtypes. Therefore the method proposed by the CEN/TC/WG6/TAG4 group is recommended for epidemiological studies and outbreaks investigations.