Estimates of prevalence of hip dysplasia in Golden Retrievers and Rottweilers and the influence of bias on published prevalence figures

Abstract

Objective—To estimate prevalence of canine hip dys- plasia (CHD) in Golden Retrievers and Rottweilers and identify sources of bias in published reports. Design—Prospective study. Animals—200 clinically normal Golden Retrievers and 140 clinically normal Rottweilers between 24 and 60 months of age referred for hip evaluation (group 1) and 93 clinically normal dogs evaluated for Orthopedic Foundation for Animals (OFA) hip certification (group 2). Procedure—Hip-extended pelvic radiographs from group 1 dogs were screened for CHD. Radiographs were evaluated twice; the first interpretation used an OFA-type subjective 7-point scoring system, and the second included the caudolateral curvilinear osteo- phyte as an additional sign of degenerative joint dis- ease. The OFA submission rate of group 2 dogs was determined from the number of official reports returned from the OFA. Results—Prevalence of CHD in Golden Retrievers ranged from 53% to 73% and in Rottweilers ranged from 41% to 69%. Among dogs referred for OFA eval- uation, radiographs from 49 (53%) were submitted to OFA. Of submitted radiographs, 45 (92%) were nor- mal; of radiographs not submitted, 22 (50%) were normal. Radiographs with normal-appearing hips were 8.2 times as likely to be submitted to the OFA. Compared with Golden Retrievers, Rottweiler radi- ographs were significantly more likely to be submit- ted for OFA certification. Conclusions and Clinical Relevance—Prevalence of CHD in these 2 breeds may be much higher than pre- viously reported in the United States. Results suggest substantial bias in the OFA database, which causes lower estimates of prevalence of CHD. (J Am Vet Med Assoc 2005;226:387–392)