The high sensitivity of a PCR-ELISA in the diagnosis of cutaneous and visceral leishmaniasis caused by Leishmania infantum

In general, the conventional techniques available for the diagnosis of leishmaniasis have relatively low sensitivity. This means that parasite-rich samples (which can usually only be collected by very invasive methods, such as bone-marrow aspiration) must be employed. This problem has not yet been solved even by use of the PCR-based techniques currently available. However, a new PCR-ELISA has been developed for the diagnosis of cutaneous (CL) and visceral leishmaniasis (VL) caused by Leishmania infantum. This assay appears to have sufficient sensitivity to be effective in the diagnosis of VL not only when bone-marrow aspirates are investigated but also when the samples are of peripheral blood. Overall, the ability of the PCR-ELISA to detect Leishmania, in 76 samples (22 of peripheral blood, 36 bone-marrow aspirates and 18 skin samples) from 72 patients living in a endemic region, was better than that of culture or the examination of Giemsa-stained smears. For example, L. infantum kDNA was detected by PCR-ELISA in 15 (83%) of the 18 skin samples from suspected cases of CL, whereas the combined use of several classical techniques only confirmed the presence of amastigotes in five (28%) of these samples. Similarly, only 21 individuals were diagnosed as having VL by conventional techniques whereas 30 were found Leishmania-positive in the PCR-ELISA. The new PCR-ELISA also appears to be a suitable technique for detecting leishmanial kDNA in samples of peripheral blood from cases of L. infantum-HIV co-infection. The assay is more sensitive than the combined use of several conventional techniques in the diagnosis of subclinical VL, probably because those with subclinical infection have relatively low parasitic loads that are generally undetectable using the other techniques.