Application of an improved method for the recombinant k 39 enzyme-linked immunosorbent assay to detect visceral leishmaniasis disease and infection in Bangladesh

Clin Diagn Lab Immunol. 2005 Dec;12(12):1410-5. doi: 10.1128/CDLI.12.12.1410-1415.2005.


Several serology-based immunoassays are used to diagnose visceral leishmaniasis (VL), a chronic protozoan parasitic disease caused by the Leishmania donovani complex. These tests are primarily designed to diagnose the most severe clinical form of VL, known as kala-azar. However, leishmanial infection is frequently asymptomatic and may manifest only as a positive serologic response or positive leishmanin skin test. We modified a previously described enzyme-linked immunosorbent assay (ELISA) that detects patient antibodies reactive with the recombinant Leishmania protein K39 (rK39) to confirm suspected kala-azar and to detect asymptomatic infection in a community study in Bangladesh. With the inclusion of a standard curve on each ELISA plate, the rK39 ELISA was more repeatable (kappa coefficient of agreement=0.970) and more reliable compared to the original method (kappa=0.587, P<0.001). The cutoff point for a positive antibody response was chosen based on the 99th percentile of the ELISA distribution for the negative-control sera. However, we found that sera from all patients with active kala-azar yielded values more than twice the magnitude of this cutoff. Using receiver-operator characteristic curves, we determined a second cutoff value predictive of kala-azar. Using these criteria, the sensitivity and specificity of the modified ELISA for kala-azar were 97.0% and 98.9%, respectively, for sera from our study population. We hypothesize that individuals with antibody levels greater than the 99th percentile of the negative controls but less than the cutoff point for kala-azar have asymptomatic leishmanial infections.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Protozoan / blood*
  • Antigens, Protozoan / immunology*
  • Bangladesh
  • Enzyme-Linked Immunosorbent Assay / methods*
  • Humans
  • Leishmania donovani / immunology*
  • Leishmaniasis, Visceral / diagnosis*
  • Leishmaniasis, Visceral / immunology
  • Protozoan Proteins / immunology*
  • Recombinant Proteins
  • Sensitivity and Specificity


  • Antibodies, Protozoan
  • Antigens, Protozoan
  • Protozoan Proteins
  • Recombinant Proteins
  • K39 antigen, Leishmania