Alveolar macrophage graded hemosiderin score from bronchoalveolar lavage in horses with exercise-induced pulmonary hemorrhage and controls.

The objective of this study was to determine if a quantitative scoring system for evaluation of hemosiderin content of alveolar macrophages obtained by bronchoalevolar lavage provides a more sensitive test for the detection of exercise-induced pulmonary hemorrhage (EIPH) in horses than does endoscopy of the lower airways. A sample population composed of 74 Standardbred racehorses aged 2-5 years was used. Horses were grouped as either control (EIPH-negative) or EIPH-positive based on history and repeated postexertional endoscopic evaluation of the bronchial airways. Bronchoalveolar lavage was performed and cytocentrifuge slides were stained with Perl's Prussian blue. Alveolar macrophages were scored for hemosiderin content by a method described by Golde and associates to obtain the total hemosiderin score (THS). Test performance criteria were determined with a contingency table. All subjects had some degree of hemosiderin in the alveolar macrophages, regardless of group. The distribution of cells among the different grades followed a significantly different pattern for the control group versus horses with EIPH (P < .05). When using a THS of 75 as a cutoff point, the THS test was found to have a sensitivity of 94% and a specificity of 88%. The level of agreement beyond chance, between the EIPH status and the THS test result was very good (Cohen's kappa = 74%). The conclusion was made that careful assessment and scoring of alveolar macrophages for hemosiderin by means of the Golde scoring system shows promise as a more sensitive approach than repeated postexertional endoscopy alone to detect EIPH.