Measurement of IgG concentration in bovine colostrum by immunoturbidimetric assay in comparison to ELISA-based assessment

Objective The aim of the presented study was to compare the results of IgG measurements using a turbidimetric immunoassay (TIA), a newly developed laboratory-independent method for direct immunoglobulin determination in colostrum, with measurements obtained via enzyme-linked immunosorbent assay (ELISA). Material and methods In colostrum samples from 59 cows, IgG concentration was measured using TIA and ELISA. Results Correlation analysis according to Pearson revealed a correlation coefficient of r = 0.74 (p < 0.0001) between the 2 methods. The Bland-Altman analysis showed that measurement by TIA resulted in significantly lower mean IgG levels than the ELISA-based quantification. This difference was more pronounced in high IgG concentration ranges. By means of a double-logarithmized data transformation it was calculated that the TIA-determined IgG-values on average amounted to 66.4 % of the IgG-values measured by ELISA. Although colostrum with low IgG concentration could be quantified with satisfactory reliability (sensitivity 100 %), high-quality colostrum was not sufficiently assessed in the TIA-based IgG measurements (specificity 40.4 %).