Diagnostic tests for kala-azar: a multi-centre study of the freeze-dried DAT, rK39 strip test and KAtex in East Africa and the Indian subcontinent

Abstract

Three diagnostic tests for visceral leishmaniasis (VL), the freeze-dried direct agglutination test (FD-DAT), the rK39 dipstick and a urine latex antigen test (KAtex), were evaluated for use in primary care in East Africa and the Indian subcontinent. Clinical suspects were prospectively recruited and tissue, blood and urine samples were taken. Direct microscopic examination of tissue smear, and FD-DAT, rK39 and KAtex were performed. Sensitivity and specificity with 95% credible intervals were estimated using Bayesian latent class analysis. On the Indian subcontinent both the FD-DAT and the rK39 strip test exceeded the 95% sensitivity and 90% specificity target, but not so in East Africa. Sensitivity of the FD-DAT was high in Ethiopia and Kenya but lower in Sudan, while its specificity was below 90% in Kenya. Sensitivity of the rK39 was below 80% in the three countries, and its specificity was only 70% in Ethiopia. KAtex showed moderate to very low sensitivity in all countries. FD-DAT and rK39 can be recommended for clinical practice on the Indian subcontinent. In East Africa, their clinical use should be carefully monitored. More work is needed to improve existing formats, and to develop better VL diagnostics.

Evaluation of rK-39 Strip Test Using Urine for Diagnosis of Visceral Leishmaniasis in an Endemic Region of India

“…These results corroborated well with the finding of other studies that reported results from the Indian subcontinent, East Africa, and Brazil. 42,43 However, all the false-positive serum samples by rK-39 strip from endemic and other infectious diseases were also tested by blood PCR using leishmaniaspecific primers from the kinetoplast DNA minicircle. 15 They were all negative, whereas 10 randomly chosen confirmed VL cases remained positive by blood PCR.…”

Current diagnosis and treatment of cutaneous and mucocutaneous leishmaniasis

“…Immunochromatography-based rapid tests and DAT are in this category. They have been used for the diagnosis of visceral leishmaniasis with variable performance [75], but it may not be possible to use the rapid tests in particular, due to the lower antibody titer in tegumentary leishmaniasis. DAT revealed species specificity-related performance [70] and therefore it may be impractical in areas where different species prevail unless reactivity to different species were to be tested at the same time.…”

Kala-azar Epidemiology and Control, Southern Sudan

“…Nongovernment healthcare providers and Government of Southern Sudan-administered healthcare facilities thus had to confi rm suspected kala-azar by direct agglutination test before they could receive a supply of the fi rst-line treatment-sodium stibogluconate-from WHO through Pharmaciens sans Frontières. The use of the direct agglutination tests was required because of concerns about the sensitivity and specifi city of the rK39 dipsticks in East Africa; a recent study suggests that these concerns were well founded (9). Also, many facilities that had received dipsticks were not using them.…”