INCREASED WHOLE-BLOOD PLATELET-AGGREGATION IN PATIENTS WITH RAYNAUDS-PHENOMENON WITH OR WITHOUT SYSTEMIC-SCLEROSIS

Platelet activation may have a pathophysiological role in Raynaud's ph enomenon (RP). However, previous studies have shown conflicting result s. This may be related to patient selection and the choice of platelet function assay. In this study, we have assessed platelet function of 30 patients with severe RP with (n = 14) or without (n = 16) systemic sclerosis (SSc), using a whole blood platelet aggregation (PA) assay. Raynaud's medication or other drugs which may affect PA were stopped a t least 2 weeks previously. Spontaneous whole blood PA and that induce d by 0.5 muM adenosine diphosphate and 0.6 and 1 mug/ml collagen were significantly increased in both groups of patients when compared with controls. There were no significant differences in PA between the 2 gr oups of patients. Using a more physiological assay, patients with seve re RP, whether or not associated with SSc, were shown to have abnormal ly increased platelet activity. Hyperactive platelets may further impe de blood flow in RP.