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What do hip and elbow screening results mean?
Health screening is primarily performed to give breeders the opportunity to select healthy animals with good conformation for breeding, without unnecessarily excluding dogs from the genetic pool.
In the UK, the vast majority of radiographs for Hip & Elbow screening will be submitted to the British Veterinary Association's Hip and Elbow Dysplasia Schemes for scoring. The new RKC Breed Health Standard stipulates that results of other schemes will be internally recorded, but only BVA scores will be published on the RKC website and count towards the 'Best Practice' category.
BVA hip scoring system (score 0-106)
The X-ray image is examined for features of 1) hip laxity and 2) degenerative changes. Based on nine radiographic features, each hip is separately assigned a numerical score from 0 to 53, with a total score of 0 to 106. It is usually reported as a total score, as well as listing both hips separately, e.g. total score of 3 (0/3) or total score of 21 (10/11).
The lower the score, the less evidence of Hip Dysplasia (and possibly arthritis) was found on the X-ray images.
BVA elbow scoring system (score 0-3)
The X-ray image is examined for features of elbow dysplasia and degenerative changes. Each elbow is separately assigned a numerical score from 0 to 3, and the higher of the two scores is then reported as the result. If one elbow scores 2 and the other 1, the result would be a score of 2.
The lower the score, the less evidence of Elbow Dysplasia was found on the X-ray images.
How are Hip screening results interpreted?
Before looking at the interpretation of hip and elbow screening results in Havanese, it is important to acknowledge that a test based on humans making a judgement by looking at images is inevitably an imperfect system, subject to observer variability. To manage this risk of bias, schemes in different countries have taken steps towards a degree of standardisation, and use multiple observers. The BVA for example has two scrutineers look at each radiograph, whereas the OFA uses three scrutineers selected at random from their pool of specialists. The grading or scoring methods used vary globally, meaning that results may differ depending on the scheme used, and consequently breeding recommendations may also be different in different countries. The BVA hip scoring system, as above, can result in a wide range of numerical scores. Their recommendation is that, within a breed, only dogs with scores in the more favourable half of the results (i.e.not above breed median score or BMS) are considered for breeding. This has served many breeds with a high prevalence of degenerative hip disease well, with improvement of hip scores over time, and the scheme is considered a success. However, there are currently insufficient numbers of tested Havanese in the BVA database to provide breeding recommendations. The same applies to the Australian database, which uses the same system as the BVA. The RKC primarily consulted the OFA database statistics before deciding to recommend BVA Hip and Elbow screening as an optional health test for Havanese in the Breed Health Scheme. The OFA uses a categorisation of hip results into ‘normal’, ‘borderline/indeterminate’ and ‘hip dysplasia’. Their ‘normal’ bracket is equivalent to BVA scores of 0-18, and in the interim, before we have a meaningful volume of data on Havanese in the BVA database, this may be a reasonable guide. It is fairly easy to determine, by whichever grading system is used, which hips are definitely good or definitely bad. Nobody would argue against excluding dogs with signs of arthritis on their screening radiographs from breeding. The challenge is with those where there is no evidence of arthritis, but varying degrees of hip laxity, particularly in a breed with no convincing evidence of a high prevalence of early onset degenerative hip disease. As a Breed Club, the HCGB will need to have a dialog with the RKC Health Team and their specialists on how to implement Hip & Elbow screening without a detriment to our genetic pool.
For comparison of Hip grading schemes in different countries, click below.