Table 1.

Details on the calculations used in the ELISA analyses, the cut-off values employed and the correlation between the ELISA results and antibody levels

ELISA	Optical density (OD) measured at	Calculation used	Positive results	Correlation between ELISA value and antibody level
BRSV	450 nm	PP = SampleCOD /PCOD X100	PP ≥ 10	Positive
BPI3V	450 nm		PP ≥ 10	Positive
BCoV	450 nm		PP ≥ 10	Positive
BHV-1 gE	650 nm	S/N ratio = SampleOD/N2	S/N ≤ 0.6	Negative
BHV-4	450 nm	S/P ratio = (SampleOD – N1)/(P1-N1)	S/P ≥ 0.3	Positive
BVD	450 nm	S/P ratio = (SampleOD – N2)/(P2-N2)	S/P ≥ 0.3	Positive
H. somni	450 nm	S/P ratio = (SampleOD – N3)/(P3-N3)	S/P > 0.6	Positive

Note that the subsequent computation applied to the raw Optical Density (OD) result can differ between ELISA kits and has been designed to give optimal diagnostic performance. Therefore the different comparison parameters (e.g. S/N, S/P or PP values) used here are inherent to the test rather than to the pathogen

COD = corrected optical density (calculated by subtraction of the mean OD value for the negative control)

Positive control (P₁), Mean of 2 (P₂) or 3 (P₃) positive controls

Negative control (N₁), Mean of 2 (N₂) or 3 (N₃) negative controls