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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF AN INTEGRATED RISK MODEL FOR FOODBORNE ZOONOTIC PARASITES IN SWINE Title: Statistical evaluation of test accuracy studies for Toxoplasma gondii in food animal intermediate hosts

Authors
item Gardner, Ian - UNIV CA DAVIS,CA
item Greiner, M - BMMU BERLIN, GERMANY
item Dubey, Jitender

Submitted to: Zoonoses and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2009
Publication Date: February 10, 2010
Citation: Gardner, I.A., Greiner, M., Dubey, J.P. 2009. Statistical evaluation of test accuracy studies for Toxoplasma gondii in food animal intermediate hosts. Zoonoses and Public Health. 57:82-94.

Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. There is little information on validity of serological tests used for diagnosis of Toxoplasma infection. In the present scientists from University of California and the Beltsville Agricultural Research Center report on the procedures to test the validity of serological tests.The results will be of interest to biologists, parasitologists, and veterinarians.

Technical Abstract: 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 paper, we review statistical approaches to evaluation of tests for toxoplasmosis with and without a gold-standard (reference) test emphasizing the use of quantitative results to avoid the inherent loss of information that comes from dichotomization of results. We use previously-published data from a comparison of 5 serologic tests for swine toxoplasmosis to demonstrate suggested methods of data analysis. We make recommendations for design and reporting of test evaluation studies for T. gondii in food animals based on our own experiences and those of others.

Last Modified: 11/26/2014