Beta-mercaptoethanol-modified ELISA for diagnosis of visceral leishmaniasis

• Published in: Journal of medical microbiology Vol. 55; no. Pt 9; pp. 1193 - 1196
• Main Authors: Abass, Elfadil M, Mansour, Durria, El Mutasim, Mohamed, Hussein, Muna, El Harith, Abdallah
• Format: Journal Article
• Language: English
• Published: England 01.09.2006
• Subjects: Agglutination Tests; Animals; Antibodies, Protozoan - blood; Antigens, Protozoan - chemistry; Antigens, Protozoan - immunology; Enzyme-Linked Immunosorbent Assay - methods; Humans; Immunoglobulin G - blood; Leishmania donovani; Leishmania donovani - immunology; Leishmaniasis, Visceral - diagnosis; Mercaptoethanol - pharmacology; Reducing Agents - pharmacology; Sensitivity and Specificity; Statistics as Topic
• ISSN: 0022-2615; 1473-5644
• DOI: 10.1099/jmm.0.46643-0

Following antigen preparation procedures similar to those of the direct agglutination test (DAT), an IgG ELISA employing intact beta-mercaptoethanol (beta-ME)-treated Leishmania donovani promastigotes was developed. The performance of the beta-ME ELISA thus developed was assessed in patients with confirmed visceral leishmaniasis (VL), revealing slightly lower sensitivity (39/40=97.5%) than that of the DAT (40/40=100%). When challenged with sera of individuals with non-VL conditions, including leukaemia and African trypanosomiasis, the specificity of the beta-ME ELISA was 100% (158/158), compared to 98.8% (156/158) for DAT. In an endemic population (n=145) manifesting a clinical suspicion of VL, results obtained with the beta-ME ELISA were highly concordant with those of DAT, both in the seropositive (65/68=95.6%) and seronegative (77/80=96.3%) groups. Furthermore, the incorporated intact antigen demonstrated higher sensitivity in ELISA (16/18=88.9%) than the water-soluble equivalent (13/18=72.2%). The stability of the formaldehyde-fixed antigen (2 months at 4 degrees C) in beta-ME ELISA, as well as the option for direct testing of whole-blood samples and visual reading of results (within 2 h, compared to 18 h for DAT), advocate the simultaneous application of the technique with DAT for confirmation of VL in laboratories with limited facilities.