Submitted to: American Society for Veterinary Clinical Pathologists
Publication Type: Abstract Only
Publication Acceptance Date: 11/19/1999
Publication Date: N/A
Technical Abstract: Marked poikilocytosis, including schistocytes and irregularly spiculated acanthocytes, were noted in red blood cells (RBCs) from calves experimentally infected with E. coli O157:H7. A method was needed to improve evaluation of RBC morphology and to quantify the poikilocytosis in 6 calves (newborn to 4 mo old) prior to and 12 calves after infection. Data were collected using a digital imaging system. Area and crofton perimeter were measured and used to calculate a shape factor for each RBC. A shape factor >1.24 was significantly different from 1.00 (perfectly round). The percentage of cells with shape factor >1.24 was compared between infected and control calves. For visual assessment, 1000 RBCs were evaluated independently (DW and CA) and enumerated for degree of poikilocytosis as: none to 4+ (numerous). Crenation (type I echinocytosis) was characterized separately as a percentage of RBCs examined. Cattle, especially newborn calves, have RBCs that are prone to poikilocytosis either as an artifact or as a result of switching from fetal to adult hemoglobin in the neonatal period. Crenation of RBCs caused the greatest discordance between the visual assessment and the digital imaging scores. Samples with a higher percentage of crenation often had a higher percentage of cells with a shape factor >1.24 than samples with 3+ or 4+ poikilocytosis (acanthocytes and schistocytes). The digital imaging system was sensitive to the cumulative effects of shape changes, such as crenation that may occur as an artifact, and may not specifically detect diagnostically significant RBC shape changes such as acanthocytes or schistocytes.