There have been a number of threads on clearances and breeding lately, and the geneticist in me is looking for some ink, so here goes.

Note: Most tests have other purposes in addition to their value for breeding decisions - this discussion is only about breeding and is not meant to diminish the importance of any tests that have value outside of breeding such as for diagnostic and treatment decisions.

From a breeding perspective, any test, clearance or other analysis is a tool that is only as good as how well it predicts what will happen in the next generation and beyond.

Take hip clearances, for example. A PennHip score gives you information on a certain dog's hips, and how likely it is that that particular dog might develop hip dysplasia in the future. Without furthur information about relatives, the score itself is not of help in making breeding decisions. So, you need to know how well a PennHip score in a dog will predict the PennHip scores in the first and future generations. The same goes for OFA hip scores. Right now it's a little easier to ferret out the information in the OFA database by looking at vertical pedigrees, but the predictability is still not great - even breeding excellent to excellent still gives you about 5% dysplastic.

Other tests are similarly flawed for breeding - elbow, patella, heart, even CERF.

The reasons for this difficulty has to do with the heritability of the trait itself and how much of the trait's expression is due to environmental and other factors.

However, when you get to genetic tests, the accuracy is much higher, especially when you are not using a marker test. PRA testing is nearly 100% accurate. Far more accurate at predicting results in future generations than x-rays, ascultations, dopplars, eye exams, etc.

To make this more meaningful from a real life perspective, think about this: When you do a breeding where at least one of the parents is Optigen A, you can feel extremely confident that none of the puppies will develop the form of PRA that the test was designed for. If those same parents both have clear CERFs, you can feel somewhat confident that the puppies will have clear CERFS. If both parents have OFA good hips, you will still worry that your pick puppy might not pass OFAs. We've all heard of seemingly random incidences of elbows not clearing even with generations of clear elbows.

Identifying PRA carriers is no longer a witch hunt - now these carriers (or even affecteds) can be used in breeding programs without stigma - as long as the other half of the equation is not a carrier. The same cannot be said about dogs that have produced hip dysplasia, cataracts, heart problems, or any of the other things that we do clearances for.

I firmly believe that PRA testing should be added by the LRC to the requirements for a Labrador to obtain a CHIC number. I also believe that PRA status should be the first question asked about any breeding. If at least one parent is not genetically clear, there is no point discussing the breeding even if the parents are both OFA excellent, clear elbows, CERF, patellas, heart, BISS and BIS winners, and perfect in any and every other way.

And by all means, don't stop doing the rest of the clearances simply because their accuracy is not perfect - they are the best we have available!

You just nailed it on the head. What you said makes more sense then almost anything posted on the forum.
I commend you and your way of thinking.
About the Optigen being a requirement for the CHIC is somthing that will not happen yet. I think you would have to talk too higher up on that. I think the problem lies with the proof of how Optigen got there evidence of the testing of the test itself. That is what I heard from the powers higher up in OFA and that was a year ago.
I have to go on OFA and see if they list Optigen free or if you have to pay for it. That should be the first step in what you said. The other thing to do would be to write the LRC,Inc. itself, because they are the ones that let the CHIC know what should be listed to make up a CHIC.

Field bred labs don't see the PRA like the bench bred labs. We have CNM- Centronuclear Myopathy. Like PRA, it is carried as a simple recessive gene. It is slightly more complicated to get the test done (swabs have to be shipped to France), but it is accurate and a very important tool for breeders. I feel that it too should be added to obtain CHIC.

Thanks Nancy.
What are your thoughts on heart clearance?

Thank you for that insightful post. I'm currently in the research stage in pursuit of a quality breeder. Health is my number one issue. So question: Do you have any idea what percentage of lab breeders utilize PRA testing?

Also, my last dog developed arthritis on his lower spine around age 11. The vet said it wasn't hip dysplasia. Do you know of any tests that might predict this problem?

thanks

All of the breeders I know make sure that at least one parent is Optigen A (clear of PRA gene.)

As for the spinal arthritis - sounds like normal aging. 11 is a ripe age for a Labrador.