In Search of an Ideal Test for Diagnosis and Prognosis of Kala-azar

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.

Key words: Diagnosis, Laboratory; Direct agglutination test; KAtex; rK39 strip test; Visceral leishmaniasis;
India

DOI: 10.3329/jhpn.v28i3.5557

J HEALTH POPUL NUTR 2010 Jun;28(3):281-285