Platelet coagulant activities in diabetes mellitus. Evidence for relationship between platelet coagulant hyperactivity and platelet volume

Abstract

Platelets have been shown to be capable of initiating and promoting some of the reactions in intrinsic coagulation and have been implicated in the pathogenesis of vascular lesions in diabetes mellitus. We have examined the contribution of platelets to the coagulation reactions in 39 patients having diabetes mellitus with and without retinopathy [background retinopathy (BR) or proliferative retinopathy (PR)], 18 patients with nonvascular eye diseases (patient controls), and 38 normal subjects. As compared to control patients, significant elevations were noted in four of the five assays for platelet coagulant activities in diabetic patients with PR and in three of five assays in patients with BR. Thus platelet coagulant hyperactivity is present in diabetics with retinopathy. Significant elevations were noted in two of the assays in patients without retinopathy (NR), suggesting that platelet coagulant hyperactivity may not necessarily be secondary to the vasculopathy. The predominant abnormalities noted were in assays reflecting the contribution of platelets to the early stages of intrinsic coagulation rather than to later stages of prothrombin activation. In addition, the mean platelet volume was found to be significantly greater in patients with PR and BR but not NR than in normal controls. A positive linear correlation (r = 0.81) was noted between the mean of the coagulant activities and platelet volume in diabetic subjects, suggesting a hitherto undescribed relationship between platelet coagulant activities and platelet volume.