Immunohistochemistry to identify Leishmania parasites in fixed tissues

The definitive diagnosis of leishmaniasis currently depends on the identifi cation of characteristic amastigote morphology in tissue, or isolation of p romastigotes by culture. Histopathological identification can be difficult and is variably sensitive; culture is considered "the gold standard", but i s not uniformly diagnostic or available. In this study, we compared light m icroscopic immunohistochemistry (IHC) using a monoclonal anti-Leishmania an tibody (G2D10) to standard hematoxylin and eosin (H&E) stain in the diagnos is of Leishmania on skin. Sixty-one archived specimens from patients suspec ted of being infected with Leishmania were used; 41 of these had leishmania sis confirmed by culture. Although not statistically significant, both sens itivity and specificity were higher for IHC compared to H&E: 51% (95% CI: 3 5-67%) compared to 42% (CI: 26-58%; 2p = 0.29) for sensitivity and 100% (CI : 83-100%) compared to 85% (CI: 62-97%, 2p = 0.25) for specificity, respect ively. Furthermore, because organisms could bd diagnosed by IHC at low powe r (x20-40), this assay was more rapid than H&E, in which parasite morpholog y could best be identified at oil immersion power. The G2D10 antibody has b road Leishmania species recognition, and offers promise as a simple, rapid diagnostic screen for leishmaniasis. Further study is underway to better ch aracterize this antibody.