This kit uses the principle of indirect method to detect EBVCA IgA antibody serum or plasma samples. The microwells are precoated with EB VCA antigen. After first adding serum or plasma specimens to be examined, the IgA antibodies in the specimen can be bound, and other unbound components will be removed by washing. In the second step, horseradish peroxidase (HRP)-labeled mouse anti human IgA antibody was added. Finally, the TMB substrate was added for color development. The presence of the absorbance (A value) of the EBVCA IgA antibody in the sample was determined by a microplate reader.