01924-A: Creation of Platelet Function Testing Guidelines to Enhance Diagnosis and Prognosis of Bleeding Disorders in Dogs

Grant Status: Closed

Grant Amount: $12,955.68
Dr. Shauna L Blois, DVM, University of Guelph
April 1, 2013 - September 30, 2013
Sponsor(s): Bull Terrier Club of America, Miniature Bull Terrier Club of America
Breed(s): -All Dogs
Research Program Area: Blood Disease

Project Summary

Platelets play a primary role in maintaining blood flow. Platelets normally circulate in an inactive state to avoid inappropriate blood clot formation (thromboembolism), and are able to immediately activate to arrest blood loss in the event of blood vessel injury. Abnormal platelet function can result in serious and fatal clinical complications. Decreased platelet function leads to excessive bleeding; increased platelet activity is associated with thromboembolism. Platelet function testing is of vital importance when investigating bleeding problems in dogs, to detect increased platelet activity that may lead to thromboembolism, and for monitoring response to platelet blocking drugs in dogs at risk of thromboembolism.

Repeated monitoring of platelet function is important in patients with abnormality of these cells. Rechecking a patient’s platelet function test can determine if a platelet abnormality is worsening or if therapy with platelet blockers is effective.  The ability to detect meaningful differences in serial platelet function results holds great clinical importance. Determining whether platelet function has changed on repeated measurements first requires knowledge of the variability of these assays expected in healthy dogs (in whom platelet function is not changing secondary to drugs or disease).

The aims of this study were to:

  1. Determine the variability of platelet function testing over four separate occasions in healthy dogs using three different platelet function tests
  2. Determine if platelet function tests are comparable, and if these methods are interchangeable.

In this study we found relatively high variability in most of the platelet function tests examined. This high variability has several implications for future platelet research and clinical applications. Firstly, it was determined that comparing a patient’s test result to a population-based reference interval is likely inaccurate when determining if the result is abnormal or changing for that individual. Rather, it is recommended to use an individual as its own baseline and compare future platelet test results to this baseline for more accurate interpretation. For example, prior to treating a patient with hyperactive platelet with aspirin, it would be most appropriate to obtain a pre-treatment platelet function test result. Then, to determine if the aspirin is effective in reducing platelet function, future results would be compared to the original result.

The second recommendation coming from this study is to perform testing in at least duplicate measurements to help reduce the variability caused by the testing methods themselves, thus leading to more accurate results.

With regard to the second aim of the study, we found that most of the platelet function tests did not compare well to each other and there was poor correlation between most platelet function testing methods. This will impact future research and clinical practices related to platelet testing, as tests cannot be considered interchangeable. This knowledge also stimulates future research to determine which is the best test method to detect platelet abnormalities, especially those induced by anti-platelet medication such as aspirin or clopidogrel.

In summary, day-to-day fluctuation in platelet function test results is expected as a result of biological and other sources of variability. These sources of variability appear to especially affect platelet function tests such as thrombelastograph-platelet mapping and platelet function analysis. Additionally, one platelet test should not be expected to behave in a similar manner as another, and these tests should therefore not be considered interchangeable.

Publication(s)

Blois, S. L., Lang, S. T., Wood, R. D., & Monteith, G. (2015). Biologic variability and correlation of platelet function testing in healthy dogs. Veterinary Clinical Pathology, 44(4), 503–510.

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