Field evaluation of FD-DAT, rK39 dipstick and KATEX (urine latex agglutination) for diagnosis of visceral leishmaniasis in northwest Ethiopia

Three novel diagnostic tests for visceral leishmaniasis (VL), namely FD-DAT, rK39 dipstick and KATEX, were evaluated under field conditions using 101 clinical cases suspected of having VL enrolled in a trial either by active (63 patients) or passive (38 patients) surveillance. VL was confirmed in 49 patients: 35 by both aspirate smear microscopy and NNN culture, 10 by NNN culture alone and 4 by aspirate smear microscopy alone. Based on tests performed in the field, sensitivity for FD-DAT, rK39 dipstick and KATEX was determined to be 95.3% (95% CI 82.9-99.2%), 71.7% (95% CI 56.3-83.5%) and 57.4% (95% CI 42.3-71.4%), respectively. Similarly, the specificity was determined to be 62.7% (95% CI 48.1-75.5%), 82.4% (95% CI 68.6-91.1%) and 84.3% (95% CI 70.9-92.5%), respectively. A higher sensitivity of KATEX (73.9% vs. 41.7%) and higher specificity of FD-DAT (100.0% vs. 48.6%) were demonstrated under passive case detection compared with active case detection. FD-DAT is recommended for confirmation of VL diagnosis in hospital settings, whereas its use in the field will be limited to exclude VL in clinical suspects. The sensitivity of KATEX and rK39 dipstick tests needs to be improved to promote their use as first-line diagnostic tests in the field setting of northwestern Ethiopia.