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

Abstract

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.

Evaluation of Two rK39 Dipstick Tests, Direct Agglutination Test, and Indirect Fluorescent Antibody Test for Diagnosis of Visceral Leishmaniasis in a New Epidemic Site in Highland Ethiopia

“…29 These tests have not been as widely accepted in VL-endemic settings in eastern Africa, in part because of reported lower sensitivity and specificity in published analyses. 11,12,16 However, our data suggest that in Ethiopia the sensitivity and specificity of the two most widely used rK39 rapid tests are at least as high as those of the DAT, and well within the acceptable range to be used as the first-line tool for confirmatory testing in peripheral health care facilities.…”

“…A meta-analysis of 30 studies of DAT and 13 studies of rK39 ICTs concluded that their overall diagnostic performance was good to excellent, but that rK39 ICTs had lower sensitivity and less consistent performance characteristics in eastern Africa compared with other regions. [11][12][13][14][15][16][17] Nevertheless, changes in prototypes and marketed tests over time as well as differences in study protocols complicate comparisons.…”

An rK28-Based Immunoenzymatic Assay for the Diagnosis of Canine Visceral Leishmaniasis in Latin America

“…In the last 15 years, the usefulness of novel synthetic fusion proteins, 14 as well as developments in molecular biology 10 in human diagnosis, have triggered advances and a great deal of knowledge, with more effective immunochromatographic tools, so that the use of these techniques has strengthened VL control, especially in massive screening studies, 11 inducing very significant progress in surveillance, diagnosis, and epidemiology in human VL all over the world. Serologic assays confined to human diagnosis, such as IFA.…”

“…Rapid and more efficient serological tests have been developed and validated as a tool to supplement the microscopic diagnosis. 6,7 Immunoserologic studies for VL in dogs, such as direct agglutination test (DAT), 8 indirect immunofluorescence assay (IFA), 4 enzyme-linked immunosorbent assay (ELISA), 6,7 polymerase chain reaction, 9 and immunochromatographic tests 6,7 (ICTs) were adapted from assays validated in humans, [10][11][12][13] with different levels of performance in canine VL. A recombinant fusion protein with tandem repeats of k39 kinesin regions and K26/HASPb1 when used in ELISA was found to detect high levels of antibody responses in infected patients.…”

Diagnosis of leishmaniasis

“…A latex agglutination test (KAtex, Kalon Biological, UK) for detection of this antigen in urine samples was evaluated using samples from confirmed cases and controls from endemic and non-endemic regions. This test showed good specificity (82% to 100%), but had low to moderate sensitivity that ranged from 47% to 95% [34][35][36][37][38]. Nowadays, this method is useful for the diagnosis of disease in cases with deficient antibody production.…”