NOTICE for owners of Tibetan Terriers tested for NCL

posted July 8, 2010
University of Missouri, College of Veterinary Medicine

Recently we have become aware of a problem with some of the DNA testing performed here for NCL in Tibetan Terriers. We want Tibetan Terrier owners to be aware of this, and understand what is being done to rectify the situation.

The mutation discovered for NCL in Tibetan Terriers is not in question – we are confident that we have identified the mutation responsible for NCL in Tibetan Terriers. A technical problem has recently been found with the test we use to detect the mutation. The test performed well in our original experiments when we used blood or tissue as a source of DNA; however, we now know that when we used cheek-swab samples collected on FTA cards, our old test does not distinguish between CARRIER and AFFECTED as well as was indicated in our original testing. Some CARRIER and AFFECTED results may have been misclassified.

We have re-examined the test and testing procedures, and redesigned the DNA test to more reliably distinguish between all three possible results: NORMAL, CARRIER, and AFFECTED. The original results for dogs that tested NORMAL are not in question - if your dog tested NORMAL, we are confident that this is an accurate result. We did not expect a problem with the NORMAL results, but to verify it we randomly chose 86 of the samples that tested NORMAL on the original test, and all 86 tested NORMAL with the revised test. If your dog tested NORMAL with the original test there is no reason to question the result – the NORMALs remain NORMAL.

As of July 7, 2010, we have retested all the samples that were collected by cheek swab and originally tested CARRIER or AFFECTED. We are now in the process of retesting the samples that came in as blood or tissue samples which were originally tested as CARRIER or AFFECTED, and expect to complete that in about a week. Thus far, all the samples that had tested AFFECTED with the original test have been confirmed as AFFECTED with the new test. Most of the samples originally tested CARRIER have been confirmed as CARRIER with the new test; however, some of the CARRIERS from the original test have a different result with the new test.

There were a few samples that did not have sufficient DNA to run the new test. These owners will be contacted and sent a new kit (at no charge) to collect a new sample for retesting.

Owners of all dogs that were originally tested as CARRIER or AFFECTED will be sent an email confirmation when the original results are verified to be accurate using the improved test. If the improved test shows that the original results were incorrect, a new report and certificate with the correct result will be issued. We expect to complete retesting and notification by the end of July.

We sincerely regret this problem, and will retest and confirm results with owners as quickly as possible. We value your business, and appreciate your patience as we work through this retesting process. Our thanks to Dr Ottmar Distl’s research team from the University at Hannover, Germany for pointing out this discrepancy, which allerted us to re-examine the testing procedure, find the problem, and correct it much sooner than we otherwise would have. We also thank the world-wide Tibetan Terrier community for their interest in this test, and support of the research that made the test possible.

If you have questions or concerns, you may contact us at HansenL@missouri.edu .