All assays were run in duplicate, and all assays with
a between-well coefficient of variation of $10% were
repeated, and the second result was used for data analysis.
The manufacturer’s recommended cut-off for a positive
assay in cattle, S/P $ 0.25, was used to define a positive
serum or milk ELISA result.
Sensitivity was defined as the percentage of fecal culture–
positive goats testing ELISA-positive. Specificity was
defined as the percentage of non–MAP-infected goats
testing ELISA-negative. The level of agreement between
results for serum and milk samples was determined by
calculating the Kappa value. The McNemar test was used to
compare paired population proportions of positive results
for the 2 ELISAs. Agreement levels between each of the 2
ELISAs and results of fecal culture were determined by
calculating the Kappa value. Finally, paired population
proportions of positive results were compared between each
ELISA and fecal culture results by use of the McNemar
test. All statistical analyses were done using InStat. e ELISA
results were also evaluated at the herd level. Because
ELISA S/P results by herd did not show homocedasticity
and were not normally distributed, the ANOVA Kruskal-
Wallis test was used, followed by the multiple comparative
Dunn test.