PLATELET FUNCTION IN VASOSPASTIC DISORDERS

If vasospastic disorders are associated with abnormal eicosanoid metabolism then disturbed platelet function may be observed. We have measured platelet aggregation (PAG) at 37°C to ADP (8 1:1 sequential dilutions from 10μM), collagen (2mg/l) and adrenaline (5μM) in 37 patients with Raynaud's syndrome (21 primary (RD), 9 secondary to scleroderma (RP) and 7 vibration white finger disease (VWF)) and 10 normal subjects (N). In addition we have determined the platelet aggregate ratio (PAR). PAG was expressed as the percentage fall in optical density after the addition of the aggregant. We also recorded the duration of the collagen lag phase and the concentration of ADP at which disaggregation occurred (DAC).Patients with RP showed enhanced PAG compared to normals. This reached significance for collagen lag phase (p<0.001), percentage PAG at 3 minutes to ADP 1.25μM (p<0.05) and the DAC (p<0.01). Similar differences were observed between patients with RP and VWF. Patients with RP also showed significantly enhanced PAG with regard to ADP 1.25μM (p<0.01) and the DAC, (p<0.05) compared to patients with RD. There was no significant difference in platelet function between normal subjects and patients with VWF or between normal subjects and patients with RD. Only with regard to DAC did patients with RD differ from patients with VWF (p<0.05). The differences observed in PAG were not reflected by the PAR. Patients with RP have significantly enhanced PAG when compared to all other groups. This may relate to eicosanoid metabolism and provides a rationale for treatment.