title: Influence of changes in body weight on peak vertical force in osteoarthritic dogs: a possible bias in study outcome.
abstract: OBJECTIVE
  Force platform gait analysis is a recognized clinical evaluation tool that captures and documents the in vivo pathomechanics of osteoarthritis (OA). In a clinical trial designed to evaluate the impact of 2 specific diets, an increase in body weight (BW) was observed in lame client-owned dogs. Covariance analysis was used to evaluate the interference of BW changes toward the evolution of peak vertical force (PVF) values. These secondary findings are reported in this study.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Lame dogs (n=26).
  
  
  METHODS
  Dogs with radiographic evidence of OA and low PVF values were fed with 2 specific diets for 30 and 60 days. PVF and BW were recorded at baseline, day 30 (D30), and D90.
  
  
  RESULTS
  Mean (+/-SD) PVF values (%BW) did not differ significantly over time (D0: 63.9+/-17.2; D30: 65.5+/-17.4; and D90: 66.5+/-20.1). In contrast, BW (kg) was significantly higher at D90 (41.3+/-7.9) when compared with D30 (39.9+/-8.4) and D0 (40.0+/-8.7). Upon covariance analyses, BW changes interfere significantly with PVF values already normalized in %BW (P=.013). Values of PVF adjusted using BW as a covariate were then 63.4+/-17.1 (D0), 65.0+/-17.3 (D30), and 67.6+/-20.5 (D90), whereas D90 was significantly higher than D0.
  
  
  CONCLUSIONS
  These findings highlighted the interference of changes in BW toward locomotor function of OA dogs when using PVF values normalized in %BW. Exacerbation of lameness when a gain in BW occurred was also sustained, raising a possible bias in clinical study outcomes.
  
  
  CONCLUSIONS
  A BW increase in dogs with OA could exacerbate a preexisting lameness and induce a bias in clinical trials.
authors.affiliation: Companion Animal Research Group & GREPAQ and Department of Veterinary Biomedicine, Faculty of Veterinary Medicine, Université de Montréal, St. Hyacinthe, Canada. m.moreau@umontreal.ca
authors.forename: Maxim
authors.initials: M
authors.lastname: Moreau
authors.forename: Eric
authors.initials: E
authors.lastname: Troncy
authors.forename: Sylvain
authors.initials: S
authors.lastname: Bichot
authors.forename: Bertrand
authors.initials: B
authors.lastname: Lussier
mesh_terms: D000818:Animals; D015982:Bias; D001696:Biomechanical Phenomena / Q000502:physiology; D001835:Body Weight / Q000502:physiology*; D002986:Clinical Trials as Topic / Q000662:veterinary; D018592:Cross-Over Studies; D004283:Dog Diseases / Q000503:physiopathology*; D004285:Dogs / Q000502:physiology; D005684:Gait / Q000502:physiology; D007794:Lameness, Animal / Q000503:physiopathology; D010003:Osteoarthritis / Q000503:physiopathology / Q000662:veterinary*; D011446:Prospective Studies; D015430:Weight Gain / Q000502:physiology