Comparative evaluation of commercial enzyme-linked immunosorbent assay kits for antibody monitoring of classical swine fever virus in Japanese pig herds: performance assessment of domestic and foreign kits

Classical swine fever (CSF) is a highly contagious disease in pigs, and vaccination with antibody monitoring is critical for its prevention. In this study, the effectiveness of two enzyme-linked immunosorbent assay (ELISA) kits for antibody detection against CSF virus (CSFV)-an indirect ELISA kit authorized in Japan in 2001 (N-kit) and a competitive ELISA kit additionally authorized in 2024 (I-kit)-was compared. For each ELISA kit, detection accuracy in terms of sensitivity, specificity and agreement rate, and quantitative accuracy were evaluated based on neutralizing antibody titers determined by serum neutralization tests. In addition, the impact of serum heat-inactivation at 56°C for 30 min on ELISA results was assessed. The results indicated that the I-kit showed the highest sensitivity and agreement rate in detection accuracy, whereas the N-kit showed the highest quantitative accuracy. Although blocking rates of the I-kit increased after heat-inactivation, high correlation rates between treated and untreated samples were confirmed for both kits, suggesting that heat-inactivation does not affect the final interpretation of the test results. These findings demonstrated that the I-kit is suitable for initial antibody screening in pigs due to its higher sensitivity, whereas the N-kit provides better quantitative accuracy, making it preferable for measuring antibody titers in sows. Therefore, the selection of an appropriate ELISA kit according to the purpose of antibody detection is necessary to ensure a more accurate evaluation of the effects of CSFV vaccination on preventing CSF in pig herds.