Supplementary material for: Evaluation of test characteristics of two ELISA tests applied to bulk tank milk and claw trimming records for herd level diagnosis of bovine digital dermatitis using latent class analysis

Bovine digital dermatitis (DD) is an infectious claw disease with a negative impact on animal welfare and production. Treponema spp. is the main causative agent, and infected animals produce specific antibodies. Our aim was to estimate sensitivity (Se) and specificity (Sp) of two ELISA research tests, Medicago’s ELISA test and GD Animal Health’s in-house ELISA test, for detection of DD-associated Treponema antibodies in bulk tank milk (BTM). We used BTM samples form 154 Norwegian dairy cattle herds, 96 from an expected high and 58 from a low prevalence region. Both tests were evaluated separately against herd-level (aggregated) claw trimming records extracted from the Norwegian Dairy Herd Recording System using latent class models in a Bayesian analysis. Cut-off values were selected using an explorative approach, and both non-informative priors for all parameters and informative beta priors for distribution of Se and Sp of claw trimming were explored.