Optimization of Antigen Preparation for Hemagglutination Inhibition Assay of Newcastle Disease Virus Serology.

Accurate assessment of Newcastle disease virus (NDV) antibody titers is crucial for effective poultry disease control and surveillance. This article introduces an optimized method for preparing 4 hemagglutination units (4-HAU) antigen solution, a key component of the hemagglutination inhibition assay (HI) used in NDV serological detection. Unlike conventional methods, which involve time-consuming and undefined back-titration and adjustment steps, this approach streamlines this process by accurately measuring the HA titer using an initial series of dilutions (1:3, 1:5, 1:7, and 1:9). We also provide a specific method for adjusting or reformulating based on the back-titration results, reducing the need for repeated back-titrations. In addition, we evaluated the effect of the accuracy of the 4-HAU antigen solution on serum HI titer and found that when the titer of the 4-HAU antigen was lower than 3, it resulted in the appearance of false-positive HI samples. By providing an accurate method and minimizing computational tasks, this approach increases test efficiency and reliability, contributing to improved disease surveillance and control in poultry populations.