This kit is comprised by HRP conjugate, other reagents, ELISA Microtiter plate pre-coated with the Newcastle Disease Virus (NDV) antigen. Apply the principle of enzyme-linked immunoassay (ELISA) to detect NDV-Ab in serum, plasma and yolk of poultry animals. During the experiment, add control, samples and antibody working solution into the ELISA microtiter plate, NDV-Ab will compete with the antibody working solution to bind with the antigen pre-coated on the ELISA Microtiter plate. Then horseradish peroxidase (HRP) conjugate is added to each ELISA microtiter plate well, and substrate reagent is added for color development. There is a negative correlation between the OD value of samples and the concentration of NDV-Ab. Measure the absorbance value of each well by using a microplate reader with 450 nm (630 nm) wavelength, then we can judge whether NDV antibody exist in the sample.