Evaluation of coated platelets, a subset of highly procoagulant platelets, in healthy dogs and dogs with neoplasia

OBJECTIVE To determine if dogs with neoplasia produce more coated platelets, a subpopulation of activated platelets gener-ated by dual stimulation with thrombin and convulxin, a glycoprotein VI agonist, than healthy control dogs. ANIMALS Client-owned dogs diagnosed with lymphoma (n = 19) or solid tumors (14) and healthy control dogs (14). PROCEDURES Platelets were stimulated ex vivo with thrombin and convulxin. Flow cytometry was used to quantify the percentage of coated platelets based on high levels of surface fibrinogen. To compare the percentage of coated platelets between the three groups, an ANOVA was performed followed by pairwise 95% confidence intervals (CI) adjusted for multiple comparisons using Tukey’s method. RESULTS We observed a greater mean percentage of coated platelets in dogs with solid tumors, compared with healthy control dogs, by 10.9 percentage points (95% CI: −1.0, 22.8), and a mean percentage of coated platelets in dogs with lymphoma that was less than healthy control dogs by 0.3 percentage points (95% CI: −11.4, 10.8). CLINICAL RELEVANCE This study provides the first data-based evidence that dogs with solid tumors may have a greater mean coated platelet percentage when compared with healthy control dogs, although there is overlap between groups. Fur-ther studies are needed investigating coated platelets in specific subsets of neoplasia and investigating additional mechanisms of hypercoagulability in dogs with neoplasia.