Image: Leishmania amastigotes from a smear of a patient with cutaneous leishmaniasis (Photo courtesy of University of California, Los Angeles).
The diagnostic method of choice for cutaneous leishmaniasis historically has been microscopic demonstration of the parasite and isolation of the protozoa in culture and detection of parasite DNA by molecular diagnostic methods.
However most cases of cutaneous leishmaniasis occur in areas without good health infrastructure where diagnostic laboratory facilities are limited, therefore a rapid, sensitive, and inexpensive test for the diagnosis of the disease is needed for use in rural, resource-limited, endemic settings.
Scientists at the Federal University of Ceará (Fortaleza, Brazil) collected skin biopsy samples from 75 patients with a clinical diagnosis of cutaneous leishmaniasis, from September 2011 to August 2013. Two biopsy samples were taken from the borders of ulcers (lesions) using a 3-mm disposable punch. One biopsy specimen was fixed in 10% formalin and processed for histopathology and the other specimen was used for a Press-Imprint-Smear.
For the imprint, the biopsy sample was put on a glass slide, and another glass slide was used to cover the tissue fragment sandwiched in between. On a firm surface, the tissue fragment between both glass slides was squeezed or squashed. Pressure on the middle of the slides was made, and therefore, the juice and tissue cells were spread on both slides surfaces that were in contact with the sample. Smears were air dried, fixed in methanol, stained with Giemsa, and examined microscopically using a 100 × oil immersion lens.
In 69 (92%) patients, the diagnosis of cutaneous leishmaniasis was confirmed by the identification of amastigotes by one or both methods. In 64 (85.3%) patients, amastigotes were detected by Press-Imprint-Smear. In 33 (44%) patients, amastigotes were detected by histopathology, and in 28 (37.3%) patients, amastigotes were detected by both methods. In 36 (48%) patients, parasites were seen only by Press-Imprint-Smear, and in five (6.7%) patients, parasites were seen only by histopathology. Leishmania (Viannia) braziliensis
was the only species in this area.
The authors concluded that the Press-Imprint-Smear method was quicker that the histological method as it only took about an hour and had a much higher sensitivity of 85.3% compared with histology at 44%. Considering its sensitivity, low cost, and simplicity, Press-Imprint-Smear is a valuable tool for diagnosing cutaneous leishmaniasis and potentially, other infectious diseases at the point of care in rural or resource-limited endemic regions. The study was published on August 11, 2014, in the American Journal of Tropical Medicine and Hygiene.
Federal University of Ceará