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Clinical and Diagnostic Laboratory Immunology, December 2005, p. 1410-1415, Vol. 12, No. 12
1071-412X/05/$08.00+0 doi:10.1128/CDLI.12.12.1410-1415.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Application of an Improved Method for the Recombinant K39 Enzyme-Linked Immunosorbent Assay To Detect Visceral Leishmaniasis Disease and Infection in Bangladesh
K. M. Kurkjian,1 L. E. Vaz,1,
R. Haque,2
C. Cetre-Sossah,1,
S. Akhter,2
S. Roy,2
F. Steurer,1
J. Amann,1,
M. Ali,2
R. Chowdhury,2
Y. Wagatsuma,2,¶
J. Williamson,1
S. Crawford,1
R. F. Breiman,2,||
J. H. Maguire,1,#
C. Bern,1 and
W. E. Secor1*
National Center for Infectious Diseases, Centers for Disease Control and Prevention, Division of Parasitic Diseases, Branch of Parasitic Diseases, Public Health Service, Department of Health and Human Services, Atlanta, Georgia,1 Centre for Health and Population Research, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh2
Received 29 July 2005/ Returned for modification 8 September 2005/ Accepted 15 September 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.
* Corresponding author. Mailing address: Centers for Disease Control and Prevention, Division of Parasitic Diseases, Mailstop F-13, 4770 Buford Highway NE, Atlanta, GA 30341. Phone: (770) 488-4115. Fax: (770) 488-4095. E-mail: WSecor{at}cdc.gov.
Present address: Vanderbilt University School of Medicine, Nashville, Tenn.
Present address: French Agricultural Research Centre for International Development, Animal Production and Veterinary Medicine, Montpellier, France.
Present address: Centers for Disease Control and Prevention, Office of the Director, Office of Global Health, Atlanta, Ga.
¶ Present address: University of Tsukuba, Department of Epidemiology, Graduate School of Comprehensive Human Sciences, Tsukuba, Ibaraki, Japan.
|| Present address: International Emerging Infections Program- Kenya, Kenya Medical Research Institute, Centers for Disease Control and Prevention, Nairobi, Kenya.
# Present address: University of Maryland School of Medicine, Baltimore, Md.
Clinical and Diagnostic Laboratory Immunology, December 2005, p. 1410-1415, Vol. 12, No. 12
1071-412X/05/$08.00+0 doi:10.1128/CDLI.12.12.1410-1415.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
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