Interlaboratory Evaluation of a Method for Quantification of Norovirus RNA as an Alternative Use for ISO 15216-1:2017 to Conduct Japan Baseline Survey of Oysters.

In this study, we aimed to investigate the standard method used for quantification of norovirus in oysters in Japan for the provisional adaptation of the method as an alternative to ISO 15216-1:2017, to conduct a Japan baseline survey of norovirus in oysters. For this purpose, the method provided by the Japan Committee for Standardization of Virus Detection in Food was subjected to an interlaboratory study to determine the performance characteristics of the standard method used in Japan. As a result, the theoretical limit of quantification for norovirus GI and GII in oysters by the standard method used in Japan was expected to be 1.92 and 1.85 log copies/g, respectively. The repeatability standard deviations (S) were 0.26 and 0.30 log copies/g for GI and GII, respectively, and the reproducibility standard deviations (S) were 0.47 and 0.44 log copies/g for GI and GII, respectively. Through the interlaboratory study, we specified several critical points to obtain scientifically reliable results by using the standard method used in Japan. Especially, necessity for application of using process control virus was the most crucial point that needed to be improved. In addition, there are many participating laboratories that could not handle dilution of standard and quantify or detect the viruses in the test samples. To ensure scientifically reliable test result, capacity building of laboratories and implementation of proficiency testing should be considered for future tasks in combination with an application of process control materials in the method. On the assumption that the problems revealed in this study will be solved, the standard method used in Japan would be suitable for use in Japan baseline survey of norovirus in oysters, which will contribute to the international action against norovirus in oysters, led by the EU.