title: Reliability of 400-cell and 5-field leukocyte differential counts for equine bronchoalveolar lavage fluid.
abstract: BACKGROUND
  Reliable enumeration of mast cells and eosinophils in equine bronchoalveolar lavage (BAL) fluid is important because small increases in the percentages of these cells support the clinical diagnosis of inflammatory airway disease (IAD). Increases in BAL neutrophils also occur with IAD but are not specific due to overlap between IAD and recurrent airway obstruction (RAO).
  
  
  OBJECTIVE
  The objectives of this study were to evaluate the reliability of a standard 400-cell leukocyte differential count and an alternate method evaluating 5 microscopic fields at 500× magnification in equine BAL fluid cytocentrifuged preparations.
  
  
  METHODS
  BAL samples from 60 horses with and without pulmonary inflammation were evaluated using 400-cell and 5-field leukocyte differential counting methods. Reliability of enumeration of each leukocyte type was assessed by calculating and comparing intraclass correlation coefficients (ICC). Reliability of mast cell enumeration was further evaluated by comparing ICCs of slides with different cell densities.
  
  
  RESULTS
  Reliability was higher for all cell types with the 5-field method; however, overall the difference between methods was not statistically significant. Neutrophil reliability was high (ICC > 0.90) with both methods. Adequate reliability (ICC > 0.85) for mast cells was achieved only with the 5-field method on slides with higher cell density.
  
  
  CONCLUSIONS
  Enumeration of mast cells is unreliable when the standard 400-cell differential counting method is used, whereas the 5-field method on slides with higher cell density reached acceptable reproducibility. Neutrophil percentages were highly reliable with both methods.
authors.affiliation: Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada. fernandn@ucalgary.ca
authors.forename: Nicole J
authors.initials: NJ
authors.lastname: Fernandez
authors.forename: Kent G
authors.initials: KG
authors.lastname: Hecker
authors.forename: Cornelia V
authors.initials: CV
authors.lastname: Gilroy
authors.forename: Amy L
authors.initials: AL
authors.lastname: Warren
authors.forename: Renaud
authors.initials: R
authors.lastname: Léguillette
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology*; D004804:Eosinophils; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis / Q000473:pathology*; D006736:Horses; D007958:Leukocyte Count / Q000379:methods / Q000662:veterinary*; D008173:Lung Diseases, Obstructive / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D008214:Lymphocytes; D008264:Macrophages; D008297:Male; D008407:Mast Cells