Frequently Asked Questions: clad/pra
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3. Why does OptiGen NOT certify pups classified as Normal by Parentage?
Theoretically, it would be correct to expect all descendents from a normal x normal mating to be normal for that exact genetic disease. This is true if both parents in EVERY mating are known to be genetically normal either by genetic testing or by "normal by parentage".
However, in order to confidently rely on this approach, you need to consider the requirements and risks:
Our recommendation to concerned breeders is to always test the dogs that will be bred. You can rely more on "normal by parentage" for pets or dogs that won't be bred. If pets or non-breeders are carriers, they won't have the disease.
Based on all these reasons, OptiGen does not issue certificates for "normal by parentage."
- You must start out testing all of your breeding stock and any new breeding stock brought into your kennel. You must not rely on anyone's "word" that a dog is normal.
- You must confirm parentage relationships for every descendent on an ongoing basis through parentage analysis. There is a very real rate of mistakenly identified parents, typically sires. We must stress to you that cases of faulty parentage happen to the very best of breeders. Accidents happen. Double matings happen. You can rely on "normal by parentage" only if you document actual parentage. Some breed clubs and registering organizations consider ongoing risk of non-parentage high enough to justify acceptance of only one generation of "normal by parentage."
- You must accept that there is a very low, but real rate of inaccuracy in parentage testing. Sometimes, more than one male can be considered the potential sire because their DNA is so similar. Sometimes, mistakes are made.
- Regarding PRA, we believe there is more than one form of inherited PRA in some breeds. While the prcd form of PRA (detected by OptiGen's test) is by far the cause of the majority of PRA cases, a small portion remains unidentified. There's nothing we can offer at present, but you need to be aware that a second type of PRA could show up.
- The frequency of new mutations causing an inherited disease is extremely rare, but this risk really can't be factored in for practical purposes.
- And finally, if a human error were made anywhere along the line - samples labeled incorrectly, dogs identified incorrectly, a lab or office error was made, several generations could pass before the error was recognized. Great attention to detail at every step is required.
4. Cataract Surgery - Should I consider cataract surgery for my PRA-affected dog? Should my dog get an ERG before deciding on cataract surgery to assess if there is good retina behind the cataracts?
In the past, conventional wisdom was a dog with PRA was not a candidate for cataract surgery, because its retina would not be capable of useful vision even if the cataract surgery were technically successful. This assumed two premises, which were generally accepted as true at the time. First, cataract surgery should be delayed until the cataracts were mature, and the dog was essentially blind from the cataracts. Second, complications from surgery were frequent, and success rates were "modest." However, things have changed. Success rates are higher, complication rates are lower, and the restoration of vision is better. So, a dog with PRA may in fact be a good candidate for such surgery. The decision for surgery comes down to cost vs. benefit. It could be argued that a dog with a late onset, slowly progressive form of PRA, such as prcd, and with a cataract interfering with central vision, should be considered for cataract surgery in order to best preserve whatever vision it has for as long as possible. Whether this makes financial sense is a decision for the owner. An ERG, done in a reliable fashion by an expert, will provide more information for making a fully informed cost/benefit decision regarding surgery. If the fundus (retina seen at the back of the eye) is visible, then an ERG should not be necessary. But if the fundus is not visible because the cataract is mature, then a good ERG can be useful. Overall, the best approach is to get annual CERF exams for your dog, so that a definitive diagnosis of cataract will be made before the cataract has progressed to the point of obscuring vision. Then, if surgery is considered, doing it before the cataract is mature is most helpful.
5. Do animals need to be tattooed or microchipped in order to have the test?
To be tested by OptiGen, dogs do not need to have permanent identification. However, there are situations where permanent ID is needed.
1. Permanent ID is needed for many registries; if you wish to have your dog entered in a registry, please make sure that you are providing all the information required by that registry.
2. In order to receive OptiGen’s special litter rate for multiple samples, puppies must have either a microchip or tattoo to “prevent mistaken identity” whether accidental or deliberate. Microchips can be inserted in 8-week-old pups (see "How old must my dog be to have a genetic test?")
6. How accurate is a direct mutation test?
The OptiGen direct mutation tests are exactly accurate. This means that the test gives clear readings in the laboratory; there is no issue of interpreting what we see. Numerous controls--absolute measures of accuracy--are used with every sample we process. The results for each dog will never change with age and will be the same whenever the same version of the test is repeated.
7. CERF numbers show a very low frequency of PRA in the tested breeds but OptiGen numbers show an apparently higher incidence of probable affecteds. How do you compare the numbers?
Think for a minute about the difference between a radio poll and a professional Gallup Poll. The radio poll invites listeners to "call in and tell us your opinion." Both CERF and OptiGen results are sort of like that radio poll--you "call in" if you feel like it, and only the people in "calling distance," as it were, are likely to answer.
Gathering statistics for a Gallup Poll is a science in itself. It's not easy to estimate the true frequency of any specific thing, be it disease, gene, opinion, or behavior. Statisticians go to great (and expensive) lengths to preclude any bias in counting or reporting. Sampling must be random, must not exclude any groups or classes of information, must not have a tendency to count some groups (or classes of information) more than others, must be large enough to be significant, must not rely on volunteered information, and so on.
Neither CERF nor OptiGen is set up to generate such an unbiased population survey that could define the frequency of PRA in any breed. Both CERF and OptiGen simply offer the voluntary opportunity to register or to test. Granted, each of these sets of numbers does indicate something. But they're similar to snapshots, which show just a portion of the landscape, just one tree in the forest. The numbers have to be seen in context.
8. Do you want to learn more about OptiGen?
More information can be found on our site...just type our address... www.optigen.com in the URL line of your browser.