Capillary tube is broken at the area of the white cell layer after centrifugation and then stained with Giemsa or Wright’s stain. - L. donovani, trypanosomes, and H. capsulatum (a fungus with intracellular elements resembling those of L. donovani) occasionally may be detected in the large mononuclear cells found in the buffy coat - With L. donovani, the nuclear material stains dark red-purple, and the cytoplasm is light blue. - H. capsulatum appears as a large dot of nuclear material (dark red-purple) surrounded by a clear halo. - Trypanosomes in the peripheral blood also concentrate with the buffy coat cells.