Parasite detection in patients with post kala-azar dermal leishmaniasis in India: a comparison between molecular and immunological methods.

AIMS To evaluate the sensitivity and specificity of serological, immunohistochemical, and molecular methods in the diagnosis of post kala-azar dermal leishmaniasis (PKDL). METHODS Twenty five patients with confirmed PKDL and 25 controls were included in the study. G2D10, a monoclonal antibody against Leishmania, was used for the immunohistochemical (IHC) staining of lesion sections to visualise anti-Leishmania donovani antibodies. The diagnostic usefulness of IHC was compared with enzyme linked immunosorbent assay (ELISA) with a recombinant (rk39) antigen, and a species specific polymerase chain reaction (PCR) assay, amplifying a kinetoplast minicircle DNA sequence. RESULTS IHC detected 22 of 25 PKDL cases, giving a sensitivity of 88%. The diagnostic sensitivity of both the ELISA and PCR tests was higher (96%). All of the 25 controls examined were negative in PCR, indicating 100% specificity of the test, whereas ELISA showed 96% specificity. CONCLUSIONS IHC with G2D10 significantly enhances the sensitivity of detection of PKDL over routine haematoxylin and eosin staining. ELISA with a recombinant antigen is an economical and practical assay. PCR is the most sensitive and specific diagnostic method for PKDL. The tests described would facilitate the recognition of patients with PKDL, enabling timely treatment, which would contribute greatly to the control of kala-azar.