title: Application of an improved method for the recombinant k 39 enzyme-linked immunosorbent assay to detect visceral leishmaniasis disease and infection in Bangladesh.
abstract: 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.
authors.affiliation: Centers for Disease Control and Prevention, Division of Parasitic Diseases, Mailstop F-13, 4770 Buford Highway NE, Atlanta, GA 30341, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Kurkjian
authors.forename: L E
authors.initials: LE
authors.lastname: Vaz
authors.forename: R
authors.initials: R
authors.lastname: Haque
authors.forename: C
authors.initials: C
authors.lastname: Cetre-Sossah
authors.forename: S
authors.initials: S
authors.lastname: Akhter
authors.forename: S
authors.initials: S
authors.lastname: Roy
authors.forename: F
authors.initials: F
authors.lastname: Steurer
authors.forename: J
authors.initials: J
authors.lastname: Amann
authors.forename: M
authors.initials: M
authors.lastname: Ali
authors.forename: R
authors.initials: R
authors.lastname: Chowdhury
authors.forename: Y
authors.initials: Y
authors.lastname: Wagatsuma
authors.forename: J
authors.initials: J
authors.lastname: Williamson
authors.forename: S
authors.initials: S
authors.lastname: Crawford
authors.forename: R F
authors.initials: RF
authors.lastname: Breiman
authors.forename: J H
authors.initials: JH
authors.lastname: Maguire
authors.forename: C
authors.initials: C
authors.lastname: Bern
authors.forename: W E
authors.initials: WE
authors.lastname: Secor
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000953:Antigens, Protozoan / Q000276:immunology*; D001459:Bangladesh; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D007893:Leishmania donovani / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000175:diagnosis* / Q000276:immunology; D015800:Protozoan Proteins / Q000276:immunology*; D011994:Recombinant Proteins; D012680:Sensitivity and Specificity
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C079253:K39 antigen, Leishmania