[Sensitivities of Respiratory Syncytial Virus Antigen-detection Kits Commercially Available in Japan]

Respiratory syncytial virus (RSV) antigen-detection kits are used in clinical settings in Japan. Here, we compared the sensitivities of 12 different kits that are commercially available in Japan. Notably, these kits were developed based on the principle of immunochromatography. The comparison was performed using six different test specimens：standard laboratory strains of RSV subgroups A and B, and clinical specimens of nasal aspirates from patients infected with RSV subgroups A or B. The specimens were serially diluted with medium at half log concentration, and the dilutions were applied to the kit tests. The minimum detection limit was determined for each kit and for every specimen by investigating the maximum dilution rate for acquiring positive result. The absolute minimum detection limits were calculated based on the viral RNA copy number of the specimens and the maximum dilution rate ranged from 107 to 109 copies/mL, depending on the specimens and kits. Thus, the sensitivity was revealed to differ among the viral specimens examined using each kit and among the kits used to examine each viral specimen, though the difference was not significant and revealed a maximum of only 10 times. The results were compared with the geometric mean values of the results for all 12 kits which were separately calculated for all 6 specimens. Consequently, some kits with lower or higher sensitivities to all the tested specimens were identified, suggesting that some general differences in sensitivity exist among commercially available RSV antigen-detection kits, although the differences are not significant. Of course, selecting kit with a higher sensitivity would be preferable, but no large differences in sensitivity among the available kits examined in the current study. Therefore, other factors such as cost-effectiveness, convenience, time required for testing, etc., can be taken into account when selecting a kit for use in clinical settings.