Evaluation of agreement between ELISA and virus neutralization index methods in the antibody detection against lumpy skin disease virus in cattle

Lumpy skin disease (LSD) is a highly contagious disease of cattle and buffaloes that cause considerable economic losses to the livestock industry in endemic regions. Although the virus neutralization index (VNI) is the gold standard test for the detection of LSD antibodies, the use of this test in seroepidemiology studies and serosurveillance is laborious and time-consuming. Accordingly, for serodiagnosis of capripox diseases, ELISA assay has been developed, but the lack of information about its performance and efficiency is one of the limiting factors in the use of this test in seroepidemiological studies. In this study, the diagnosis agreement between a recently developed ELISA based on P32 recombinant protein and the VNI method, as a gold standard for serological diagnosis of Capripox virus, was evaluated using 95 sera samples including 25 negative control, 14 positive control, and 56 suspected cattle sera. Result showed that all the negative control sera assessed by VNI and ELISA had no antibody titers against LSD. All the 14 (100%) positive control sera had VNI values ≥1.5 and were considered as the positive sera; however, by ELISA method, 13 samples (93%) were diagnosed as the positive. Among the 56 samples collected from LSD-suspected cattle, 16 samples (29%) were detected as the positive by VNI, whereas 13 samples (23%) were detected as the positive sera by ELISA method. There was no statistically significant difference between the percentages of negative or positive samples assessed by ELISA or VNI method (P>0.05), associated with the Kappa index value of 0.71 showing the substantial agreement. These findings indicating an acceptable agreement and performance of the developed ELISA system based on P32 recombinant protein in comparison to VNI method for diagnosing antibody against LSD virus in cattle.