| Dairy and beef cattle (n = 494) from seven Michigan farms located in the northeastern part of the lower peninsula in Michigan were used to estimate the sensitivity (Se) of the caudal fold tuberculin test (CFT), the CFT and comparative cervical test used in serial interpretation (CFTCCTSER), and gross necropsy using a 'gold standard' approach. Using all seven herds, the sensitivities of the CFT, the CFTCCTSER, and gross necropsy were 93.0% (95% CI: 80.9% to 98.5%), 88.4% (95% CI: 74.9% to 96.1%), and 86.1% (95% CI: 72.1% to 94.7%), respectively. The Se of the two skin tests was slightly higher when two or more gross lesions were present, and the Se of gross necropsy was significantly higher (P = 0.049). In addition, four two-population-two test simulation-based Bayesian models allowing for correlation between the two tests were used to estimated Se and specificity (Sp) of the CFT and CFTCCTSER, assuming that a gold standard was not available. Sensitivity and Sp of both the CFT and CFTCCTSER were estimated with results of mycobacterial culture (CULT). There were no significant correlations between CFT and CULT, but a significant negative correlation (0.218 [PCI: 0.005 to 0.731]) between CFTCCTSER and CULT. The estimates for Se and Sp of the CFT, CFTCCTSER, and CULT were 85.4% (PCI: 56.3 to 97.5), 75.8% (PCI: 47.5% to 93.0%), and 62.3% (PCI: 40.1% to 89.9%), respectively. Herd-level sensitivity (HSe) and specificity (HSp) and predictive values for (1) CFTCCTSER, (2) the overall sensitivity and specificity of serial use of CFTCCTSER, histologic exam, CULT and PCR, (3) where specificity of (2) was assumed to be 100%, and (4) which was as (3) but increasing sensitivity to 90%. An empirical distribution of number of herds and herd sizes for the northeastern lower peninsula was used for these simulations. Point estimates of HSe and HSp for the four scenarios were 75.0% and 94.0%, 71.2% and 100%, 78.3%, and 100%, and 83.3% and 100%. (Abstract shortened by UMI.)... |
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