Field evaluation of the CATT/Trypanosoma brucei gambiense on blood‐impregnated filter papers for diagnosis of human African trypanosomiasis in southern Sudan

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Abstract
Summary: Most Human African Trypanosomiasis (HAT) control programmes in areas endemic for Trypanosoma brucei gambiense rely on a strategy of active mass screening with the Card Agglutination Test for Trypanosomiasis (CATT)/T. b. gambiense. We evaluated the performance, stability and reproducibility of the CATT/T. b. gambiense on blood‐impregnated filter papers (CATT‐FP) in Kajo‐Keji County, South‐Sudan, where some areas are inaccessible to mobile teams. The CATT‐FP was performed with a group of 100 people with a positive CATT on whole blood including 17 confirmed HAT patients and the results were compared with the CATT on plasma (CATT‐P). The CATT‐FP was repeated on impregnated filter papers stored at ambient and refrigerated temperature for 1, 3, 7 and 14 days. Another 82 patients with HAT, including 78 with a positive parasitology, were tested with the CATT‐FP and duplicate filter paper samples were sent to a reference laboratory to assess reproducibility. The CATT‐FP was positive in 90 of 99 patients with HAT (sensitivity: 91%). It was less sensitive than the CATT‐P (mean dilution difference: −2.5). There was no significant loss of sensitivity after storage for up to 14 days both at ambient and cool temperature. Reproducibility of the CATT‐FP was found to be excellent (kappa: 0.84). The CATT‐FP can therefore be recommended as a screening test for HAT in areas where the use of CATT‐P is not possible. Further studies on larger population samples in different endemic foci are still needed before the CATT‐FP can be recommended for universal use.