Table 4.

Results for the general estimating equation predicting positive ELISA status (≥ 50 EU) in any one of 4 ELISA tests conducted in parallel) for an analysis of the association between ELISA status for MAP infection and age and year of study on a NZ dairy farm over 4 seasons (2013–2017)

Input variable	Coefficient	Odds Ratio (OR)	95% CI	p-valuea
Parityb
Primparous	Ref	Ref
Multiparous	0.62	1.86	1.41–2.45	< 0.001
Study year
2013–2014	Ref	Ref
2014–2015	−1.41	0.24	0.12–0.49	< 0.001
2015–2016	0.71	2.03	0.98–4.19	0.055
2016–2017	−1.11	0.33	0.14–0.77	0.010
Interaction d
Multiparous 2014–2015	0.41	1.50	0.72–3.12	0.284
Multiparous 2015–2016	−1.35	0.26	0.12–0.56	< 0.001
Multiparous 2016–2017	−0.02	0.98	0.41–2.34	0.970
ICCe		0.38	0.35–0.42
Variance within		0.063
Variance among		0.039

^aSignificance of coefficient

^bParity of cow defined as primiparous (≤ 2 years) and multiparous (> 2 years)

^cMilking season. Each season uses the preceding season as the referent

^dInteraction term between parity and milking season. Overall significance of the interaction term: < 0.001

^eIntra class correlation coefficient