Parameter estimation and use of gamma interferon assay for the diagnosis of bovine tuberculosis in Brazil1

Lopes L.B., Alves T.M., Stynen A.P.R., Mota P.M.P.C., Leite R.C. & Lage A.P. 2012. Parameter estimation and use of gamma interferon assay for the diagnosis of bovine tuberculosis in Brazil. Pesquisa Veterinária Brasileira 32(4):279-283. Embrapa Agrossilvipastoril, Rodovia MT 222, km 2,5, Caixa Postal 343, Sinop, MT 78.550-970, Brazil. E-mail: [email protected] This study aimed to evaluate the interference of tuberculin test on the gamma-interferon (INFγ) assay, to estimate the sensitivity and speci icity of the INFγ assay in Brazilian conditions, and to simulate multiple testing using the comparative tuberculin test and the INFγ assay. Three hundredifty cattle from two TB-free and two TB-infected herds were submitted to the comparative tuberculin test and the INFγ assay. The comparative tuberculin test was performed using avian and bovine PPD. The INFγ assay was performed by the BovigamTM kit (CSL Veterinary, Australia), according to the manufacturer’s speci ications. Sensitivity and speci icity of the INFγ assay were assessed by a Bayesian latent class model. These diagnostic parameters were also estimate for multiple testing. The results of INFγ assay on D0 and D3 after the comparative tuberculin test were compared by the McNemar’s test and kappa statistics. Results of mean optical density from INFγ assay on both days were similar. Sensitivity and speci icity of the INFγ assay showed results varying (95% con idence intervals) from 72 to 100% and 74 to 100% respectively. Sensitivity of parallel testing was over 97.5%, while speci icity of serial testing was over 99.7%. The INFγ assay proved to be a very useful diagnostic method.