The optical density (OD) values in wells coated with NSP 3ABC are corrected by subtracting the OD values of the corresponding wells containing the control antigen.
ODNSP 3ABC-ODControl= ODCorr
Pls. find the attached files
https://www.ncbi.nlm.nih.gov/pubmed/7949346
Page 198 in: Antonio Morilla, Kyoung-Jin Yoon, Jeffrey J. Zimmerman. 2008. Trends in Emerging Viral Infections of Swine John Wiley & Sons,Pp.387. ISBN 0470376600, 9780470376607