Dr. Christopher Riggs Letter to the Editor

The opinion/editorial by Dr. Fenger published by the Thoroughbred Daily News on 29th August 2014 Thoroughbred Daily News on 29th August 2014 contains critique on a report of a scientific study that was recently published in the Equine Veterinary Journal. Regrettably, Dr. Fenger severely misrepresents the study and her criticisms contain many errors and inaccuracies. The reputed falsities that she describes, as published by the Thoroughbred Daily News, are at the expense of the authors of the peer-reviewed scientific paper, of which Dr. Stephanie Preston was lead, of the Hong Kong Jockey Club (HKJC) and of fair and honest debate on the pros and cons of the routine use of furosemide in Thoroughbred racing in North America. 

Dr. Fenger’s opinion is based on her interpretation of the paper, which reflects a misunderstanding of the statistical techniques applied, the way in which the data was presented and how findings were reviewed in relation to existing knowledge.

Dr. Fenger claims that the study contains “many … simple arithmetical errors” and on the basis of this criticism she suggests that it is flawed. However, all but one of her criticisms is incorrect and it seems that she fails to appreciate the methodology applied. For example, table 2 of the paper, which comes under intense criticism from Dr. Fenger, presents very different information to that which she describes, despite explanation in the accompanying caption. Given the data that is illustrated (results from survival analysis), there is no reason for the sum of numbers in the right column to bear direct relation to the 822 horses included in the study. 

Dr. Fenger’s confusion over the difference between the number of horses recorded in the text as having not suffered Exercise Induced Pulmonary Haemorrhage (EIPH), 327, and the number listed in table 2 as being (EIPH) negative, 157, is accounted for by the fact that the table presents data from survival analysis. The relatively smaller number in the table is simply explained by the fact that not all horses in the study experienced the event of interest (retirement). In other words, 170 horses classified as EIPH negative did not retire within the period of study and so were not included in table 2. 

The pie chart illustrated in figure 1 is more sophisticated than Dr. Fenger appears to comprehend, despite explanation in the figure caption. The graph illustrates all horses that were subject to endoscopy (89%) and all those that were not (11%). However, the 89% that were subject to endoscopy were subdivided to graphically illustrate the subsets that were identified with EIPH (a small proportion of which also suffered epistaxis) and those that were not. Consequently, the sum of the numbers simply extracted from the graph exceeds 100. 

Dr. Fenger is correct in her observation that in one instance the number “327” was misprinted as “326”. This was a typographical error, for which the authors of the paper apologize. 

The authors of the paper went to great lengths to obtain valid information on the average number of starts undertaken by Thoroughbred racehorses in the USA. Given the scientific nature of the paper, it was important to report reliable data. The authors appreciate that there may be differences in the incidence of EIPH between different groups of horses but this should be studied systematically in order to encourage informed debate. 

Dr. Fenger has regrettably misconstrued and misrepresents the data presented in table 2 in relation to the proportion of horses that retire from racing at the Hong Kong Jockey Club as a result of EIPH. The vast majority of horses at the HKJC are retired voluntarily by owners on account of poor competitiveness. The system in place at the HKJC requires full disclosure of veterinary records and, even if retired voluntarily, veterinary-related conditions may be cited in the retirement process. A high proportion of horses that are retired voluntarily will have “EIPH” or some other respiratory condition noted in their clinical history. This does not infer that the horse was retired due to this condition but that it may have been a consideration in the owner’s decision. In reality, the proportion of horses retired specifically due to EIPH is very small and restricted to those that suffer epistaxis (blood at the nostrils) or recurrent, severe grades on endoscopy. Last season for example, only 0.9% of horses that left racing were retired specifically due to this condition. 

Similarly, in her rather sensationalist handling of the observation that 4% of all horses in training at Hong Kong suffer epistaxis, Dr. Fenger has ignored a critical aspect of the data that relates to this figure, despite it being clearly stated in the text. Published data relating to the prevalence of “bleeders” in different racing jurisdictions has previously been restricted to the proportion of starters. As Dr. Fenger notes, this is typically in the range of 0.15 to 2.41%. The figure for this same statistic at the HKJC has fluctuated between 0.3% – 0.6% over the past 10 seasons – at the low end of Dr. Fenger’s range. However, the 4% published in the paper is very different: it relates to the total prevalence in the population of horses that contribute to all starts. Given that most horses start in races on multiple occasions, the actual prevalence in the population as a whole will clearly be much higher than the figure for starters. In addition, the 4% includes all incidents of bleeding among the same horses while training – data that is simply not available in other jurisdictions. This will, of course, further increase the magnitude of overall prevalence. It should be obvious to all that directly comparing the data for starters against the figure for the population as a whole is entirely misleading 
The Hong Kong racing culture and environment provides the opportunity to implement optimum regulatory practice and the on-track, closed training complex supports a level of racing control and transparency that may be difficult to achieve elsewhere in the world. The HKJC goes to great lengths to oversee the welfare of horses racing and training in Hong Kong and to maintain integrity of the sport. All horses are subject to regular, thorough scrutiny by veterinarians employed by the Club, who have an obligation to report promptly all clinical findings. These findings are reviewed daily by independent, Regulatory Veterinarians, working with Stewards. Each horse is subject to a clinical inspection by a Regulatory Veterinarian before every race, to determine its suitability to compete. In addition, a thorough and extensive blood and urine screening programme is enforced to ensure drug-free racing and to check that only legitimate medications, which have been fully documented, are used on horses in training. The Club vigorously pursues protocols which are perceived to protect horses and improve both the safety and the integrity of the sport. For instance, horses that are recorded as suffering a single severe episode of epistaxis or any grade of epistaxis due to EIPH on more than two occasions in racing and/or training are compulsorily retired. 

The highly regulated, closely documented and open nature of racing at the HKJC is integral to facilitating studies such as that published by Dr Preston and co-workers, which are not possible in other jurisdictions.

The authors of the paper, the distinguished veterinarians and/or scientists who peer-reviewed it and the Equine Veterinary Journal understood the science behind the study and the contribution it makes to our overall understanding of the condition of EIPH. It is unfortunate that the study has been so misrepresented in your publication and I hope that this helps to set the record straight. 

Dr. Christopher M. Riggs, 
Head of Veterinary Clinical Services, 
The Hong Kong Jockey Club