Study comparing OFA to PennHip

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Postby TheRedQueen » September 13th, 2010, 10:16 am

Good stuff!

http://www.upenn.edu/pennnews/news/hip- ... tive-study

Hip Dysplasia Susceptibility in Dogs May Be Underreported, According to Penn Vet Comparative Study
September 1, 2010
PHILADELPHIA –- A study comparing a University of Pennsylvania method for evaluating a dog’s susceptibility to hip dysplasia to the traditional American method has shown that 80 percent of dogs judged to be normal by the traditional method are actually at risk for developing osteoarthritis and hip dysplasia, according to the Penn method.

The results indicate that traditional scoring of radiographs that certify dogs for breeding underestimate their osteoarthritis susceptibility. The results are of clinical importance to several populations, most notably veterinarians, breeders and pet owners.

The two hip screening methods -- the standard Orthopedic Foundation for Animals, or OFA model, and Penn Vet’s PennHIP model -- were applied to a sample of 439 dogs older than 2 years. The four most common breeds included in the study were German shepherds, Labrador retrievers, golden retrievers and Rottweilers, all breeds commonly susceptible to hip dysplasia.

According to Penn researchers, even if breeders were to selectively breed only those dogs having OFA-rated “excellent” hips -- the highest ranking but in some breeds, a very small gene pool, the study suggests that 52-100 percent of the progeny, depending on breed, would be susceptible to hip dysplasia based on the Penn Vet scoring method.

“We believe the lower rates of hip laxity detection using the OFA methods are not the fault of the expert radiologist reading the radiograph but rather a deficiency of the radiographic view,” said veterinary surgeon Gail Smith, professor of orthopaedic surgery, lead author and director of the PennHIP Program. “We believe many veterinarians are not using the best test to control a disease. In many ways this is an animal-welfare issue.”

The findings point to a weakness in current breeding practices. If breeders continue to select breeding candidates based upon traditional scores, then, according to the Penn study, breeders will continue to pair susceptible dogs and fail to improve hip quality in future generations. Despite well intentioned hip-screening programs to reduce the frequency of the disease, canine hip dysplasia continues to have a high prevalence worldwide with no studies showing a significant reduction in disease frequency using mass selection.

Canine hip dysplasia, or CHD, is defined by the radiographic presence of hip joint laxity or osteoarthritis with hip subluxation (laxity) early in life. A developmental disease of complex inheritance, it is one of the most common orthopaedic diseases in large and giant-breed dogs and causes pain and loss of mobility.

The traditional OFA screening method relies heavily on conventional hip-extended, or HE, radiographs, which the study contends do not provide critical information needed to accurately assess passive hip joint laxity and therefore osteoarthritis susceptibility.

“We suspect that all hip-screening systems worldwide based on the HE radiograph have similar diagnostic deficiencies,” Smith said. “Hopefully, our results will motivate veterinarians and breeders to consider this newer approach.”

To achieve genetic control of CHD, researchers said, an accurate test must minimize false-negative diagnoses which mistakenly permit the breeding of dogs that carry genes coding for CHD. Particularly for a late-onset disease such as CHD, dogs remaining in the gene pool must not only be free of obvious signs of CHD at the time of evaluation (2 years of age for OFA) but ideally should not be susceptible to the osteoarthritis of CHD that occurs later in life.

The PennHIP method quantifies hip laxity using the distraction index, or DI, metric which ranges from a low of .08 to greater than 1.5. Smaller numbers mean better hips. The PennHIP DI has been shown in several studies at multiple institutions to be closely associated with the risk of osteoarthritis and canine hip dysplasia. It can be measured as early as 16 weeks of age without harm to the puppy.

Specifically, the PennHIP method considers a DI of less than .3 to be the threshold below which there is a near zero risk to develop hip osteoarthritis later in life. In contrast, dogs having hip laxity with DI higher than .3 show increasing risk to develop hip osteoarthritis, earlier and more severely, as the DI increases.

Comparing the overall results of the study, 52 percent of OFA-rated “excellent,” 82 percent of OFA-rated “good” and 94 percent of OFA-rated “fair” hips all fell above the PennHIP threshold of .3, making them all susceptible to the osteoarthritis of CHD though scored as “normal” by the OFA. Of the dogs the OFA scored as “dysplastic,” all had hip laxity above the PennHIP threshold of .3, meaning there was agreement between the two methods on dogs showing CHD or the susceptibility to CHD.

The key feature of the PennHIP radiographic method is its ability to determine which dogs may be susceptible to osteoarthritis later in life. Because dogs are recognized as excellent models for hip osteoarthritis in humans, the authors are interested in the prospect of applying this technology to humans. Knowing a dog’s risk for osteoarthritis early would allow veterinarians to prescribe proven preventive strategies, like weight loss, to lower the risk of this genetic disorder. Also, dog breeders now have a more informative measure to determine breeding quality to lower the risk of hip osteoarthritis in future generations of dogs.

“In humans, with appropriate studies of course, it is conceivable that mothers of susceptible children — and there are many — may adjust a child’s lifestyle, including diet, to delay the onset or lessen the severity of this genetic condition,” Smith said.

PennHIP is currently in common use by service-dog organizations such as the U.S. Air Force, the U.S. Army and numerous dog-guide schools. There are approximately 2,000 trained and certified members currently performing PennHIP procedure worldwide.

The study was conducted by Smith, Michelle Y. Powers, Georga T. Karbe, Thomas P. Gregor, Pamela McKelvie, William T. N. Culp and Hilary H. Fordyce of the Department of Clinical Studies at Penn Vet. Culp is currently with the School of Veterinary Medicine at the University of California, Davis.

The study was funded by the University of Pennsylvania, the National Institutes of Health, The Seeing Eye Inc., the Morris Animal Foundation and Nestle Purina Co. The article was published in the Journal of the American Veterinary Medical Association.

Smith, who is the inventor, and the University of Pennsylvania, which holds the patent, have a financial interest in the PennHIP method.

A video in which Dr. Gail Smith describes this study is available at http://www.youtube.com/watch?v=VG_fJvevbJ8
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Postby mnp13 » September 13th, 2010, 11:13 am

Just a note - the study was funded by PennHip, so there was just a "little" bias in the reporting.
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Postby plebayo » September 13th, 2010, 12:47 pm

mnp13 wrote:Just a note - the study was funded by PennHip, so there was just a "little" bias in the reporting.


Haha very interesting.

Regardless of these results I am still in support of OFA all the way. We did LiLo's hip thru PennHip at 18 weeks of age. If the hips are bad you van fuse the pelvis with a JPS surgery. Her hips came back good/fine whatever their rating is. Let's see, 4 years later my dog has hip dysplasia.

I think OFA gives dogs the best chance due to making the minimum 2yrs old. Obviously doing my dog "early" gave us a false positive because her hips look nothing like they did when she was 18 weeks. I guess I have a little bias too :p
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Postby TheRedQueen » September 13th, 2010, 3:31 pm

PennHip gives numbers, not a rating. OFA gives ratings of "good, fair, etc"

I've been more pleased with those numbers (when we were testing Assistance Dogs at Fidos)...than I was with OFA ratings.

We had dogs re-tested from younger ages to older ages, and the hips didn't change a great deal...the training staff used to say..."Oh, we'll keep _____ in the program a while longer, and see if the hips *tighten* up as they get older". Never saw any change...except in one case, and they got worse. ;)
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Postby plebayo » September 13th, 2010, 4:27 pm

So I looked up LiLo's chart and she scored .29 and .30. It's just frustrating because she definitely could have benefited from having the JPS.
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Postby TheRedQueen » September 13th, 2010, 5:00 pm

plebayo wrote:So I looked up LiLo's chart and she scored .29 and .30. It's just frustrating because she definitely could have benefited from having the JPS.


But if they weren't showing up badly on radiographs...would the vet have done the procedure? Why did you have her hip films done in the first place? Were you worried at that age already? Would an OFA rating have changed things...would it have shown up differently in a different position? Why did you not get an OFA rating done instead? I'm just curious why you blame PennHip scores?
"I don't have any idea if my dogs respect me or not, but they're greedy and I have their stuff." -- Patty Ruzzo

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Postby plebayo » September 13th, 2010, 6:39 pm

TheRedQueen wrote:
plebayo wrote:So I looked up LiLo's chart and she scored .29 and .30. It's just frustrating because she definitely could have benefited from having the JPS.


But if they weren't showing up badly on radiographs...would the vet have done the procedure? Why did you have her hip films done in the first place? Were you worried at that age already? Would an OFA rating have changed things...would it have shown up differently in a different position? Why did you not get an OFA rating done instead? I'm just curious why you blame PennHip scores?



I went with Pennhip because at the time I was told it was better than OFA. They weren't showing up badly, hence we didn't do the JPS. I had the films done because at the time the vet estimated that she would be a large dog [although she only topped out at 45lbs], and due to the fact she's got possible shepherd/rotti I figured better safe than sorry. Yes OFA would have shown something because we took our first set of follow up rads when she was maybe 3yrs old. They do OFA at 2yrs so perhaps if I had done OFA it would have shown up as crappy hips. Unfortunately with the OFA you can't do JPS because JPS has to be done at 20 weeks, so in that respect OFA wouldn't change anything. But it definitely sucks thinking your dog has good hips and then having to find out their hips are really bad.

I don't like Pennhip because obviously a lot can change as a dog is growing and I really don't think taking the x-rays so young is that accurate. I mean, obviously in our case it isn't because my dog was young, we did the rads, and as she aged her hips became bad. This is why I'm really not a huge Pennhip fan.
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Postby mnp13 » September 13th, 2010, 8:09 pm

plebayo wrote:
mnp13 wrote:Just a note - the study was funded by PennHip, so there was just a "little" bias in the reporting.


Haha very interesting.

Regardless of these results I am still in support of OFA all the way. We did LiLo's hip thru PennHip at 18 weeks of age. If the hips are bad you van fuse the pelvis with a JPS surgery. Her hips came back good/fine whatever their rating is. Let's see, 4 years later my dog has hip dysplasia.

I think OFA gives dogs the best chance due to making the minimum 2yrs old. Obviously doing my dog "early" gave us a false positive because her hips look nothing like they did when she was 18 weeks. I guess I have a little bias too :p


When I read your post I thought "duh, you can't do hips at 18 weeks" so I went and looked it up... and um... evidently you can..

http://research.vet.upenn.edu/Default.aspx?TabId=3234
The looser the joint, as determined by the PennHIP method, the greater is the chance that the hip will develop DJD. (The standard hip-extended method can actually mask true hip joint laxity). There are obvious advantages to screening dogs for hip joint laxity at 4 months of age (or six months, 1 year, etc.) as opposed to waiting until 2 years of age. The reliability of the PennHIP method slightly improves with age, with one year 1 year being marginally superior to 6 months, which in turn is marginally better than 4 months. For all dogs, we recommend when possible, to use the mean (average) of repeated evaluations to get a more reliable estimate of a dog's hip laxity status (phenotype).


But they want you to do them over and over again.
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Postby TheRedQueen » September 13th, 2010, 8:34 pm

Doing the hips early helps groups that go through a lot of dogs, say, like an Asst. dog group...we used to weed them out at 4-6 months old if the hips were OBVIOUSLY bad. If they were iffy at the time, we gave them time to grow up.
"I don't have any idea if my dogs respect me or not, but they're greedy and I have their stuff." -- Patty Ruzzo

"Dogs don't want to control people. They want to control their own lives." --John Bradshaw
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Postby TheRedQueen » September 24th, 2010, 11:00 am

Another hip testing article...it's by a BC breeder, but it's very interesting too...

http://www.stilhope.com/hipartical.htm
"I don't have any idea if my dogs respect me or not, but they're greedy and I have their stuff." -- Patty Ruzzo

"Dogs don't want to control people. They want to control their own lives." --John Bradshaw
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Postby Leslie H » September 25th, 2010, 9:38 pm

Did Pennhip mention what percentage of dogs scored lower than .3? I know in the bull breeds, it's an extremely small number of dogs. And my understanding is that anything under .3, Pennhip states, is very unlikely to develop dysplasia, while anything w/a rating .7 or higher, is very likely to develop dysplasia. The median for the APBT was in the .5's I believe. What Pennhip is suggesting would pretty much eliminate the APBT gene pool.
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