Evaluation of platelet function screening tests to detect platelet procoagulant deficiency in dogs with Scott syndrome.
BACKGROUND
Clinical diagnosis of platelet dysfunction is complex and technically challenging. The wide repertoire of platelet responses requires a test panel to assess different parameters of platelet reactivity. While "global" hemostasis analyzers and whole blood assays have potential for testing platelet function, their ability to evaluate platelet procoagulant activity is ill-defined.


OBJECTIVE
The aim of this study was to determine whether platelet procoagulant deficiency, the pathophysiologic defect of Scott syndrome, could be detected in point-of-care and whole blood assays.


METHODS
Study subjects were 4 Scott syndrome-affected German Shepherds and 8 control dogs. We evaluated 2 point-of-care instruments: the platelet function analyzer (PFA-100) and thromboelastograph (TEG). TEG analysis was performed on recalcified citrated whole blood with and without tissue-factor activation. A whole blood flow cytometric assay was configured to detect thrombin-induced platelet P-selectin expression and platelet-derived microparticle release. Cytometric samples were analyzed after 1 hour and 1 day of storage.


RESULTS
We found no significant differences between Scott and control dogs in PFA-100 COL/ADP closure times or in any TEG parameter in tissue-factor-activated samples. In nonactivated samples, mean clotting time (K) and time to maximal rate of thrombus generation were significantly prolonged in Scott dogs; however, values overlapped with those of control dogs. Cytometric analysis of samples from Scott dogs showed significantly diminished platelet-derived microparticle release. Samples from all dogs reanalyzed after 1 day of storage had nonspecific increases in basal P-selectin expression and vesiculation.


CONCLUSIONS
A whole blood cytometric assay to detect stimulated platelet microparticle release can be used to screen for Scott syndrome. However, platelet activation artifacts preclude overnight storage for next-day analysis.
Brooks
Marjory B
MB
Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY, USA. mbb9@cornell.edu
Randolph
John
J
Warner
Karen
K
Center
Sharon
S
D000818:Animals; D001772:Blood Cell Count / Q000662:veterinary; D001778:Blood Coagulation Disorders / Q000097:blood / Q000662:veterinary*; D001779:Blood Coagulation Factors / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism / Q000473:pathology; D004283:Dog Diseases / Q000097:blood*; D004285:Dogs; D005260:Female; D005340:Fibrinogen / Q000378:metabolism; D005434:Flow Cytometry; D008297:Male; D019007:P-Selectin / Q000378:metabolism; D015539:Platelet Activation / Q000502:physiology; D010979:Platelet Function Tests / Q000295:instrumentation / Q000662:veterinary*; D019095:Point-of-Care Systems
D001779:Blood Coagulation Factors; D019007:P-Selectin; C049426:platelet procoagulant factor; D005340:Fibrinogen