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.牛指（趾）间皮炎（Bovine digital dermatitis, DD）是一种传染性蹄病，对动物福利与生产性能均具有负面影响。密螺旋体属（Treponema spp.）为其主要致病菌，感染动物可产生特异性抗体。本研究旨在评估两款酶联免疫吸附试验（Enzyme-Linked Immunosorbent Assay, ELISA）研究级检测试剂盒——梅迪卡哥（Medicago）公司ELISA检测试剂盒与GD动物健康（GD Animal Health）自研ELISA检测试剂盒——在散装罐奶（bulk tank milk, BTM）中检测与DD相关的密螺旋体抗体的灵敏度（Se）与特异度（Sp）。本研究共纳入154个挪威奶牛群的散装罐奶样本，其中96份采自预估高流行区域，58份采自低流行区域。以从挪威奶牛群记录系统中提取的牛群水平（聚合）蹄部修剪记录作为参照，采用贝叶斯分析（Bayesian analysis）中的潜类别模型（latent class models）对两款检测方法分别进行独立评估。截断值通过探索性方法确定，同时本研究探索了两类先验分布：所有参数的无信息先验，以及针对蹄部修剪检测的灵敏度与特异度分布的信息性β先验（beta priors）。