Message from Dr Aine Seavers:
Could you all do me a big favour and get this notice out to all the Basenji journals/breeders/newsletters asap.
THYROID BLOOD TESTS IN BASENJI- PLEASE STOP DOING T4 THYROID TESTING BY ITSELF!!!
T4 –thyroxin IS A Total WASTE OF MONEY, TOTALLY USELESS AND POSSIBLY DANGEROUS FOR THE INDIVIDUAL BASENJI AND THE BREED AS A WHOLE.
I have been following 14 animals over 3 years since the 2006 -115 dog collection, collecting more blood and thyroid biopsy results and thanks to these dedicated owners, we now are much more confident to state;
1) Whilst cTSH blood tests especially retested 4-6 months later really do tell us a lot about the thyroid state of the Basenji- the tT4 and the fT4 blood tests by themselves tell you nothing of any validity.
1b) In fact, tT4 – thyroxin mis-interpreted can lead to a dog being placed on un-necessary medication, unwarranted removal from a breeding pool and an unfair prognosis on survival if the animal was suffering a severe illness at the time of the blood test.
2) The only time T4 should be tested is alongside a cTSH, or to retest drug therapy after 3 months or to be checked in rhTSH stimulation testing.
3) PLEASE ALWAYS CHECK AN ANIMAL’S cTSH BEFORE MAKING ANY TREATMENT OR BREEDING DECISIONS, not its tT4 levels.
I will endeavour to write a full clinical paper on this over the next year.
I am trying to see if I can get some ultrasounds done on a large number of breeding dogs to give breeders a better concept of what is the status of their Basenjis so watch this space for an update there as well.
I am very concerned that newer breeders are hearing we did original work with NSW Club in 2006 and coming to the conclusion that hypothyroidism must be an issue when the paper proved it was not so to the degree it was being proposed to so be.
Results of Comprehensive Thyroid Research
Hypothyroidism is considered to be most of the most commonly diagnosed endocrine disorders in the canine. Quite possibly this hormonal disease is also the most over mis-diagnosed condition as a definitive diagnosis of Hypothyroidism, especially in the absence of clinical signs, can be difficult because of the lack of readily available blood tests with a high degree of accuracy and specificity. It is further recommended that these Thyroid function tests should only be performed in dogs with actual clinical signs consistent with Hypothyroidism. The situation is thus further complicated when a specific Breed Society decides to start screening in advance for Hypothyroidism on the basis of an alleged possible inherited component to the condition. Driven by” abnormal” results based on a non-breed specific laboratory range without any actual signs of disease, the situation can rapidly escalate wherein perfectly healthy breeding stock are removed from the gene pool on the basis of such testing. The gene pool of Basenji in Australia is dramatically smaller in comparison to a gene pool for GSDs in USA. Any reduction in the size of the Basenji gene pool has the potential to dramatically affect the future of the breed and not necessarily for the good of the breed. Anecdotally, there are reports of close to 80% of the breed in some countries being medicated on the basis of a non breed specific blood result. In addition, no follow-on testing 3 months later to check for pre- and- post- pill TT4rrSH levels would appear to be encouraged, thus condemning some animals to a life-time of potentially unnecessary medication. Often the incorrect “Hypothyroid diagnosis” is being made routinely in animals as young as four months of age!!
Even if this breed were truly widely susceptible to Hypothyroidism, with most Basenji progeny almost all free of orthopaedic conditions such as HD, or any major concerns re cardiac, optical or dermatological disease states, consideration could be given to tolerating the late onset of an easily controlled late age onset condition such as Hypothyroidism. Withdrawing valuable breeding stock or losing 4 years of breeding life, on the basis of one abnormal thyroid blood in the absence of clinical signs, might well prove catastrophic for the breed. The Cavalier King Charles breed Society in the United Kingdom tolerates low expression of Chiari syndrome on that basis. This despite the fact that the syringomelia is a much more dramatic, expensive and painful condition for breeders dogs and vets to control.
If a breeder is forced to make a decision that affects such a gene pool, the decision must to be an informed decision based on solid scientific fact and parameters. Such information has previously not been available.
The Basenji Club of NSW, in conjunction with Symbion Laboratory and with Vet surgeons across Australia who deal with the breed, all collaborated to subsidise a nationwide blood draw to collect and collate such information. A Basenji Breed Specific Blood Screen was created and analysed in an attempt to provide the most economically and easily accessible tests for the Basenji Club to amass information that would allow the breeders to begin to make informed decisions.
The exact results have been submitted as scientific paper for consideration of publication by the Australian Veterinary Journal as a peer-review paper in order to validate the values and conclusions. If accepted, the full paper will be made available to all Basenji Clubs in the coming months.
What we can say so far is that our survey suggests that previously established canine reference range values for TT4 may not be appropriate for use in Basenji.
Consideration should be given to interpreting serum thyroid TT4 values against a breed specific range such as that available via Symbion Laboratories.
It is to be recommended that all future thyroid testing for Basenji include a minimum of a Thyroid Stimulating Hormone assay (cTSH) alongside any TT4 or FT4 blood tests.
In addition a higher range of normal values would also be wise to adopt for interpretation of Cholesterol and Haematocrit values for the breed.
The higher “normal” cholesterol does how give some concern in very elderly Basenji where we are investigating a possible link with CV As( often described as a type of “Stroke”) and the cholesterol level. This previously unknown link is currently under further investigation.
TSH dynamic stimulation testing is still held by many to be the gold standard for thyroid status determination; the reality is that the expensive test is rarely performed now having been replaced by the above T 4/cTSH ratio due to the latter’s availability and ease of use.
Human thyroid stimulating hormone (ThyrogenR Genzyme Corporation) has now replaced the bovine or chemical grade TSH as a safer and effective test for dynamic testing where the T4!TSH/Chol are inconclusive. However the cost of the actual test kit is exorbitant- about $3000. One also has to know the normal T 4 values before this test can be interpreted correctly so it was impractical to perform this test until we first established the breed norm. A small number of Basenji throwing a cTSH over 0.6nglml were tested in May however thanks to an extra-ordinarily generous donation from Denncare Australia who purchased a kit of rhTSH product specifically to test these Basenji. Denncare company asked for nothing in return, they just simply wanted vets and owners to have more information to make better diagnoses and avoid un necessary medication. Royal Canin also provided $500 to help subsidise the laboratory fees for this additional May testing for which the Oak Flats Vet clinic were covering the cost.
Thyroid biopsy was declined at the time of the first survey due to the invasive nature of extracting the gland. However, a Basenji Thyroid Gland Histo-Bank has now been set up to where the thyroid gland of any deceased Basenji can be sent and then analysed by a panel of expert pathologists when sufficient numbers and funding are available. Owners are also invited to include punch biopsies of the skin to be submitted at the same time. The samples are currently being submitted to and paid for by my own clinic-Oak Flats and will be processed as I can afford so there may be a delay of months before the results of an individual animal would be known. If however any owner wished to submit the gland to the Clinic and pay for their own dog at the same time then the results would be available within 7 days.
There is also now some good progress with the availability of DNA testing and this is a route the Clubs across Australia can consider exploring to find even better screening tests for their animals.
The Screen 1 results of this breed-specific survey indicate that caution ‘needs to be employed in hound breeds such as the Basenji when interpreting results against a non- breed specific range. As a profession, Vets should be encouraging breed societies to collect breed specific data especially DNA data. In the absence of such data, great care should be exercised before prescribing medication to a healthy animal in the absence of clinical signs simply on the basis of one blood test result at one moment in time. Vets and Breeders should also exercise caution when classifying breeding stock as defective again on the basis of one single type or one single set of test results as would appear to be the case with some TgAA results.
The authors would like to acknowledge the financial support from The Basenji Club of NSW and participating Basenji owners, to Symbion Laboratories, Applecross, Dungog, Hammett St, Maitland VH, Oak Flats VC, Princes Hwy VC, Richmond, Stud Park Vet, Strathbogie, Tallangatta, VetWest Hilarys, Vineyard VC and Vet Path W A for donation of their time and expertise in collecting the samples and to the Basenji Club Executive along H. Church, and T & O Robb for helping co-ordinate the project.