Abstract
Geographical and racial differences in the incidence of thrcmbo-embolisn could be related to basic dissimilaritiesin the haemostatic system in different ethnic groups. However reliable comparative population studies in haemostatic parameters is lacking. The large expatriate ccmnunity in Saudi Arabia offers such a chance.
Subjects tested were all healthy blood donors (aged 20-50 years) and were classified on the basis of ethnic origininto three categories (1) Arabs n=750, (2) Westerns (Americans and Europeans) n=400, and (3) S.E. Asians (Filipinos) n=570. The measurements done included PT, PTT, TT, Reptilase time, Plasma fibrinogen, AT III, Plasminogen, F.VIII:C, FX, α-2 Antiplasmin and Platelet aggregation in response to ADP (20.0, 2.0, 1.0, 0.5 & 0.25 uM), Collagen, Arachidonic acid, Adrenaline and Ristocetin (1.5, 1.2 & 1.0 mg/ml).
There were no significant ethnic differences in the measured plasmatic clotting tests. This contrasts the finding of many smaller studies. Besides no significant ethnic differences were noted in platelet aggregation response to high doses of ADP (20 uM) or Ristocetin (1.5 mg/ml) and to Collagen. However, 45% of the S.E. Asians displayed abnormally inhibited responses to Adrenaline when compared to Arabs (34%) and Westerns (35.2%). Asians also displayed more inhibited responses to lower doses of ADP (2.0 & 1.0 uM) . On the other hand, S.E. Asians showed the lowest incidence of inhibited Arachidonic acid responses (9%) when compared to Arabs (24%) and Westerns (26%) . Similar racial differences were noted in response to low doses of Ristocetin (1.2 & 1.0 mg%) where Arabs and Asians showed high incidence of abnormally reduced responses (26-28%) when compared to Westerns (15%). No evidence of enhanced aggregation could be detected in Westerns. Changes of climate and/or dietary habits could be important factors influencing the haemostatic system in such a way that reduces ethnic dissimilarities.