Sensitivity, specificity and predictive values of immunochromatographic strip test in diagnosis of childhood kala-azar

In Bangladesh, the total population at risk for kala-azar exceeds 20 million (18%) living in 88 Thana (19%) of 27 districts (42%). A confirmatory diagnosis of visceral leishmaniasis (kala-azar) is done by demonstration of the parasite (LD body) in organ aspirates or tissue biopsy sample, an invasive procedure with relatively low sensitivity. To assess the diagnostic usefulness of ICT for antibody against the leishmanial antigen rK39 & its feasibility for use under field conditions (rural areas). An experimental study conducted during January, 2003 to July, 2003 in pediatrics department of MMCH including 60 confirmedly diagnosed KA cases & 60 controls having diseases other than KA. One drop of peripheral blood is applied to the nitrocellulose strip & 3 drops of test buffer is added to the dried blood. Observing 2 visible bands indicates presence of IgG anti-K39. The rK39 strip test was positive in 57 out of 60 confirmed KA case diagnosed by LD body demonstration in splenic or bone marrow aspirate. The estimated sensitivity was 95%. One control diagnosed as other than KA had positive strip test but negative aspirate smear. The estimated specificity of the strip test was 98.3%. The predictive value of a positive result is 98.3% & that of a negative result is 93.5%. rK39 strip test is highly sensitive & specific in our situation & it can be used as a simple & the best method for diagnosis of KA in rural areas.