01066-A: Predictive Serum Biomarkers for Canine Endurance Exercise

Project Summary

Absolute fitness for athletic events of long duration is difficult to determine in advance, since it is a practical impossibility to pre-conduct an event lasting 10-14 days. Therefore, veterinarians and mushers rely on pre-exercise physical examinations and routine blood testing to detect illnesses that might preclude the successful completion of such events. These procedures permit the exclusion of some dogs, but up to 50% of dogs that start ultra-endurance races such as the Yukon Quest or Iditarod are dropped (removed from the team to be transported back to the home kennel) prior to completion of the race. Although some of these dogs are dropped due to acquired injuries that are inevitable in an athletic event, some of these dogs may fail to complete the event due to subtle illness or lack of adequate conditioning that nevertheless falls within the boundaries of "normal" physiology. Our hypothesis was that within a narrowly-defined population (i.e., racing sled dogs preparing to compete in an ultra-endurance event), the definition of "normal" could be tightened to identify dogs that, although clinically normal, did not have sufficient conditioning to complete such an event. To test this hypothesis, we employed routine blood testing of dogs less than I week prior to the start of the 2008 Yukon Quest, and using these values matched to the eventual outcome of the individual dogs (dropped vs. completed), constructed multivariate formulas that predicted the outcome of the dogs based on their pre-race blood testing. This analysis constructed 6 different, but strikingly similar, predictive formulas. In all cases, the formulas contained the pre-race values for markers of muscle damage (the lower, the better), and some measurement of red blood cell concentration (the higher, the better), despite the fact that in all cases, these values were within the published normal ranges for dogs. When a probability of 0.4 (40% predicted chance to complete the event) was used as a cut-off value, all dogs with values below the cut-off did not complete the race (100% or perfect negative predictive value). These results will be validated with a second set of blood samples taken immediately before the 2009 version of the Yukon Quest to determine whether these formulas are sufficiently robust to be applied to all events of this type and assist mushers in identifying the dogs most suitable for competition.

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