Bouvier - OFA Reliability

Posted by Adrienne

OFA Reliability Study

Re-Posted with permission

While the discussion continues as to the benefits of the methods of evaluating hip dysplasia, I would like to present some new and exciting information regarding the reliability of the OFA method.

In the Journal of the American Veterinary Medical Association, Vol. 211, No. 9, November 1, 1997, there appears an article entitled, "Reliability of early radiographic evaluations for canine hip dysplasia obtained from the standard ventrodorsal radiographic projection," by E. A. Corley, DVM, Ph.D., G. G. Keller, DVM, MS; J. C. Lattimer, DVM, MS, M. R. Ellersieck, Ph.D. This peer reviewed article reports the results of a study to determine the reliability of preliminary hip evaluations performed by the OFA on dogs between 3 and 18 months of age. The results suggest that preliminary OFA evaluations of hip joint status are generally reliable.

The study involved 2,332 dogs 624 Golden Retrievers, 724 Labrador Rerievers, 528 German Shepherd Dogs, and 456 Rottweilers. It compared preliminary evaluations for dogs in three age groups, 3 to 6 months of age (mean age 4.8 months), 7 to 12 months (mean age 10.4 months), and 13 to 18 months (mean age 15.4 months), with later definitive evaluations performed on the same dogs when they were between 24 and 31 months of age.

The study showed that a preliminary evaluation of EXCELLENT was 100% reliable; a preliminary evaluation of GOOD was 97.9% reliable; a preliminary evaluation of FAIR was 76.9% reliable; a preliminary valuation of MILD was 84.4% reliable; and a preliminary evaluation of MODERATE was 97.4% reliable. There was only one dog with a preliminary evaluation of severe which was definitive in later evaluation.

This is exciting information for breeders and owners. As stated in the

article, "The economic value of early screening of dogs for etermination of hip joint status is obvious. The study reported here uggests that the test method used by the OFA, and generally accepted worldwide, is an appropriate method for early mass screening of hip joint status." The article also reported the results of a study of the stress radiographic method for diagnosis of hip dysplasia (commonly referred to as the PennHIP method), the data from which shows that it is less reliable than the OFA method. It referenced an article by Dr. Gail Smith, et al., presenting the results of a longitudinal study of the PennHIP method. (Smith GK, Gregor TP, Rhodes WH, et al). "Coxofemoral joint laxity from distraction radiography and its

contemporaneous and prospective correlation with laxity, subjective score, and evidence of degenerative joint disease from conventional hip-extended radiography in dogs." (Am J Vet Res 1993; 54:1021-1042)

The results of Dr. Smith's study show that 12% of the dogs evaluated as normal at 4 months of age by the PennHIP method, i.e., a distraction index of less than or equal to 0.3, were later determined to have degenerative joint disease; and 48% of the dogs evaluated as abnormal at 4 months of age, 57% of the dogs evaluated as abnormal at 6 months of age, and 38% of the dogs evaluated as abnormal at 12 months of age by the PennHIP method, i.e., a distraction index of greater than 0.3, did not have evidence of degenerative joint disease at 24 months of age.

Another study (Lust G, Williams AJ, Burton-Wursten N, et al., "Joint laxity and its association with hip dysplasia in Labrador Retrievers" (Am J Vet Res 1993; 54:1990-1999) showed that a distraction index less that 0.4 is 88% reliable for predicting normal hip joint phenotype and a distraction index greater than or equal to 0.4 is 57% reliable for predicting canine hip dysplasia.

One additional fact I found interesting was that 1.5 million radiographic

evaluations by 35 radiologists were analyzed in this study of the OFA method, and there was agreement 94.9% of the time as to whether the dog should be classified as having normal, borderline, or dysplastic phenotype. In addition, there was agreement 73.5% of the time on the same hip grade (excellent, good, fair, borderline, etc.). The report stated, "This percentage of agreement is high considering the subjective nature of the evaluation and supports use of the definitive evaluation as a criterion standard. The high percentages of agreement on 1.5 million evaluations (pause for a second and think about this astounding number of evaluations) is another basis for the reliability of the OFA method."

I am sorry I didn't do something about getting this article out to all of you and the other members of our Club after I read it. When I saw the discussion on hip dysplasia, I realized that this information may not have been made available to you. I think it is interesting, and it should give all of us increased confidence in the OFA method.

JAVMA has been requested for permission to reprint this article in the GRNews. I believe the more timely information we can obtain to help us breed better dogs, the faster we will succeed. As our President, Joyce Kinghorn, stated in a recent post, "We all need to know every result of every study."