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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

From: Risk factors associated with exposure to bovine respiratory disease pathogens during the peri-weaning period in dairy bull calves

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
  1. 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
  2. COD = corrected optical density (calculated by subtraction of the mean OD value for the negative control)
  3. Positive control (P1), Mean of 2 (P2) or 3 (P3) positive controls
  4. Negative control (N1), Mean of 2 (N2) or 3 (N3) negative controls