Comparison of indirect and modified agglutination tests for detection of antibodies to Toxoplasma gondii in domestic cats

Toxoplasma gondii is a protozoan parasite with worldwide distribution. The accurate detection of this zoonotic agent in cats and other hosts has public health importance. Blood samples from 89 domestic cats were tested for antibodies to T. gondii using 2 commercial agglutination test kits, an indirect (IHAT; Toxo-HAI FUMOUZE; Fumouze Diagnostics) and a modified (MAT; Toxoscreen DA; bioMerieux) agglutination test. Antibodies were found in 16 of 89 (18%) cats by the IHAT and in 23 of 89 (26%) cats by the MAT, with an overall agreement between the 2 serologic tests of 92% (kappa = 0.77; i.e., substantial agreement beyond chance). Considering the MAT as the gold standard, the IHAT showed perfect relative specificity (100%) and lower relative sensitivity (70%). The suboptimal sensitivity of the IHAT limits its use in epidemiologic studies in cats.