Abstract
The latex agglutination test (KAtex), direct agglutination test (DAT), and the rK39 immuno-chromatographic strip test (dipstick test) were evaluated for their role in the diagnosis and prognosis of visceral leishmaniasis (kala-azar) in India. Sera and urine samples from 455 subjects--150 confirmed visceral leishmaniasis cases, 160 endemic controls, 100 non-endemic controls, and 45 other febrile diseases--were included in the study. The sensitivity of the KAtex, DAT, and rK39 strip test was 87% [95% confidence interval (CI) 80-96], 93.3% (95% CI 88-100), and 98% (95% CI 93-100) respectively. The specificity of these tests was 98% (95% CI 93-100), 93% (95% CI 87-100), and 89% (95% CI 82-97) for the KAtex, DAT, and rK39 strip test respectively. Fifty cases were followed up and subjected to the KAtex, DAT, and rK39 strip test after 30 days of successful treatment. The DAT and rK39 strip test showed positive results in all the 50 cases whereas the KAtex showed no positive reaction in any case. Based on the results, it is concluded that the sensitivity and specificity of the DAT and rK39 strip test are comparable but the greater convenience of use of the strip test makes it a better tool for the diagnosis of visceral leishmaniasis in the peripheral areas of endemic regions whereas the sensitivity of the KAtex needs to be improved to promote its use as a first-line diagnostic test in the field-setting. It may be used for the prognosis of the disease as antigen becomes undetectable in urine after 30 days of the completion of the treatment. Alternatively, it can be used as an adjunct with rK39 for sero-epidemiological surveys.
Highlights
Leishmaniasis is endemic in 88 countries spread over five continents, with an estimated yearly incidence of 1-1.5 million cases of cutaneous leishmaniasis and 500,000 cases of visceral leishmaniasis (VL)
The sensitivity of the KAtex, direct agglutination test (DAT), and rK39 strip test was 87%, 93.3%, and 98% respectively
The present study was conducted on 455 subjects for the field evaluation of the KAtex, DAT and rK39 strip test as a diagnostic and prognostic tool for kala-azar
Summary
Leishmaniasis is endemic in 88 countries spread over five continents, with an estimated yearly incidence of 1-1.5 million cases of cutaneous leishmaniasis and 500,000 cases of visceral leishmaniasis (VL). It requires invasive procedure to find the parasite in the tissue, i.e. spleen, bone-marrow, and lymph-node. It is the gold standard for the diagnosis of VL, the procedure is cumbersome, time-consuming, technically demanding, risky, and very difficult to apply in field conditions or remote places/primary health centres. To obviate these procedures, various serological tests have been developed, evaluated, and tried. Various serological tests have been developed, evaluated, and tried These tests have the advantage of being safe, are less invasive, and can be carried out in large numbers of samples. Aside from practical difficulties at peripheral laboratories, the sensitivities and specificities of most of the above tests have been the limiting factors
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