Statistical evaluation of test accuracy studies for Toxoplasma gondii in food animal intermediate hosts

The availability of accurate diagnostic tests is essential for the detection and control of Toxoplasma gondii infections in both definitive and intermediate hosts. Sensitivity, specificity and the area under the receiver-operating characteristic (ROC) curve are commonly used measures of test accuracy for infectious diseases such as toxoplasmosis. These test performance characteristics are important considerations when selecting from among a group of tests for a specific testing purpose. In this study, we reviewed statistical approaches to evaluation of tests for toxoplasmosis with and without a gold-standard (reference) test, including use of ROC analysis and likelihood ratios which retain the diagnostic information inherent in a quantitative test result. We use previously published data from a comparison of the accuracy of serological tests for swine toxoplasmosis to demonstrate suggested methods of data analysis. We make recommendations for statistical analysis and reporting of test evaluation studies for T. gondii in food animals based on our own experiences and those of others.