Acute Phase Proteins in Racehorses with Inflammatory Airway Disease

Background: Systemic inflammation is observed in horses with heaves and could also be present in horses with a lesser degree of pulmonary inflammation. Hypothesis/Objectives: It was hypothesized that racehorses with inflammatory airway disease (IAD) have increased concentration of circulating acute phase proteins. The objective of this study was to compare serum acute phase proteins of racehorses with and without lower airway inflammation. Animals: Serum from 21 client-owned Standardbred racehorses with exercise intolerance and lower airway inflammation and serum from 10 client-owned Standardbred racehorses with exercise intolerance without lower airway inflammation. Methods: In a case-control study, serum samples from previously characterized horses presented for exercise intolerance with or without lower airway inflammation based on bronchoalveolar lavage fluid cytology were analyzed for serum amyloid A protein (SAA), C-reactive protein (CRP), and haptoglobin using commercial ELISAs. Results: There was no significant differences between groups for SAA (non-IAD versus IAD, median (range): 3.47 (0.06-34.94) versus 6.33 (0.06-80) mu g/mL, P =.49), CRP (10.87 (2.05-29.03) versus 4.63 (0.02-31.81) mu g/mL, P =.23) or haptoglobin (900.36 (607.99-2018.84) versus 749.54 (530.81-1076.95) mu g/mL, P =.09). Conclusions and Clinical Importance: In this population of poorly performing racehorses in training, serum SAA, CRP, and haptoglobin were not helpful in distinguishing between horses with IAD from horses with exercise intolerance from other causes.