This characteristic formed the basis of an erythrocyte sedimentation rate test that was done with special sedimentation tubes. Prominent rouleaux formation results in rapid erythrocyte sedimentation in whole blood samples allowed to stand undisturbed. Prominent rouleaux formation in species other than horses, cats, or pigs should be noted as an abnormal finding. 11,532 Rouleaux formation can also occur in association with some lymphoproliferative disorders in which one or more immunoglobulins are secreted in high amounts ( Fig. 132 Increased concentrations of globulin proteins-including fibrinogen, haptoglobin, and immunoglobulins-potentiate rouleaux formation in association with inflammatory conditions. 37,443,460 Rouleaux formation also depends on the presence of high-molecular-weight proteins in plasma. 37 Erythrocytes that are more deformable and have greater membrane fluidity with less negative charge on their surfaces (weaker electrostatic repulsive force) aggregate more readily than cells with the opposite characteristics. Rouleaux formation depends on both the nature of the erythrocytes and the composition of plasma. Harvey DVM, PhD, DACVP, in Veterinary Hematology, 2012 RouleauxĮrythrocytes on blood films from healthy horses, cats, and pigs often exhibit rouleaux (aggregations of erythrocytes grouped together like a stack of coins) formations (see Fig. 1 However, these aqueous stains are superior to conventional methanolic Wright or Wright-Giemsa stains in the staining of distemper inclusions in canine blood cells. A significant limitation of the Diff-Quik stain and other aqueous stains, such as Hema 3 (Fisher Scientific, Pittsburgh, PA) and the stain used in the automated stainer Aerospray 7120 (Westcore, Inc, Logan, UT), is that they do not stain basophil, mast cell, or large granular leukocyte granules well ( Fig. The Diff-Quik stain is classified as an aqueous stain, even though the fixation is done in methanol, because the component stains were prepared in water. The quality of Diff-Quik-stained blood films is generally somewhat lower than that obtained by longer staining procedures, but staining quality is improved by allowing the blood film to remain in the fixative for several minutes. Various rapid stains, such as Diff-Quik (Dade Behring Inc., Newark, DE), are available. This material can appear as a precipitate between cells in blood that resembles stain precipitation ( Fig. Carboxymethylcellulose has been infused into the peritoneal cavity of horses and cattle in an attempt to prevent abdominal adhesions after surgery. Precipitated stain may be present because the stain or stains needed to be filtered, the staining procedure was too long, or the washing was not sufficient. The presence of stain precipitation can make identification of leukocytes and blood parasites difficult ( Fig. 30ĭrying or fixation problems can result in variably shaped refractile inclusions in the erythrocytes these may be confused with erythrocyte parasites ( Fig. Blood films prepared from blood collected with heparin as the anticoagulant have an overall magenta tint owing to the mucopolysaccharides present. 30 Blood films may have an overall blue tint if stored unfixed for long periods before staining or if the unfixed blood films are exposed to formalin vapors, as occurs when blood films are shipped to the laboratory in a package that also contains formalin-fixed tissue. If the methanol contains more than 3% water, morphologic artifacts including loss of cellular detail and vacuolation may be present. 30īlood films should be fixed in methanol within 4 hours (preferably within 1 hour) of preparation. High pH, prolonged staining, or insufficient washing can result in excessively blue-staining blood films. Low pH, inadequate staining time, degraded stains, or excessive washing can result in excessively pink-staining blood films. These staining characteristics depend on the pH of the stains and the rinse water as well as the nature of the cells present ( Fig. The azure dyes stain acids, resulting in blue to purple colors, and eosin stains bases, resulting in red coloration ( Fig. Romanowsky-type stains are composed of a mixture of eosin and oxidized methylene blue (azure) dyes. Harvey DVM, PhD, DACVP, in Veterinary Hematology, 2012 Romanowsky-Type Stainsīlood films are routinely stained with a Romanowsky-type stain (e.g., Wright or Wright-Giemsa) either manually or using an automatic slide stainer.
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