Serodiagnosis of sleeping sickness in the Republic of the Congo: comparison of indirect immunofluorescent antibody test and card agglutination test

The card agglutination test for trypanosomiasis (CATT) was evaluated and compared to the classical immunofluorescent antibody test (IFAT) in the immunological diagnosis of Gambian trypanosomiasis. Tests were performed on serum and whole blood. Cross-reactions were found in the CATT with sera from patients suffering from parasitic infections other than sleeping sickness, but could be largely overcome by selecting 110 as the specific threshold dilution. At 140 dilution no false positive result was observed in the IFAT. At the specific threshold dilution, the sensitivity of IFAT was 94·7%, compared with 91·6% for the CATT. On whole blood, a more convenient sample in the field, IFAT specificity (100%) was greater than that of the CATT (94·3%), as was its sensitivity (92% compared with 82·5%). In view of its simplicity and rapidity of execution, the CATT is an efficient serological test to detect new foci. When greater sensitivity is required, IFAT should be preferred to CATT.