Evaluation of an EDTA version of CATT/Trypanosoma brucei gambiense for serological screening of human blood samples.

CATT/Trypanosoma brucei gambiense, a direct card agglutination test designed for field surveys on human African trypanosomosis, is currently used with freshly collected heparinized blood samples. When testing serum samples, it has been observed earlier that, at lower sample dilutions, a complement-mediated inhibition phenomenon may cause false negative test results. This can be avoided by adding an anticomplementary agent such as di-sodium ethylenediaminetetraacetate dihydrate (EDTA) to the reaction. As the sensitivity of the blood assay might be improved in the same way, this possibility has been examined under both laboratory and field conditions, by adding EDTA to the test buffer or, as an anticoagulant, to the blood samples. The CATT-EDTA versions proved up to 7% more sensitive but also 1-2% less specific than the current test. CATT buffer supplemented with EDTA remained stable for at least 2 years at +45 degrees C.