Diagnosis of human visceral leishmaniasis by PCR using blood samples spotted on filter paper

The polymerase chain reaction (PCR) is a simple, rapid procedure that has been adapted for the diagnosis of leishmaniasis. In the present study, 85 blood samples and seven bone marrow aspirates from 85 patients with clinical symptoms suggestive of visceral leishmaniasis from the metropolitan region of Belo Horizonte in the Brazilian State of Minas Gerais were screened using molecular and serological techniques. Samples that were negative (N = 12) and positive (N = 19) in parasitological and serological tests were used as controls. Of the 85 samples analyzed by PCR, 61 (71.7%) showed the expected amplification products in agarose gels. However, when the technique was combined with molecular hybridization, 72 samples (83.5%) gave a positive signal on film. Nineteen patients with Leishmania parasites in bone marrow cultures (positive controls) showed PCR hybridization in whole-blood samples, as did the seven bone marrow aspirates positive for Leishmania. None of the negative controls reacted in PCR or in an indirect immunofluorescent assay. These results indicate that PCR could replace the conventional parasitological examination in the diagnosis of leishmaniasis since it provides very satisfactory results with blood samples spotted on filter paper.