RESUMEN
Platelet aggregation test was assessed by the turbidimetric method in 52 normal Thai adults consisting of 24 males and 28 females with ages ranging from 20 to 50 years. The aggregating agents used were adenosine diphosphate (ADP), adrenaline and collagen. It was found that the ranges of threshold concentration of ADP, adrenaline and collagen which gave maximal induction of platelet aggregation were 5-10 microM, 2.5-10 microM and 0.14-0.28 mg/mL, respectively. Collagen at the above concentration, showed lag phase within 2 minutes. This corresponds to that described in the reference method. Moreover, when induced by ADP and adrenaline 53-65 per cent and 81-87 per cent of the subjects, respectively, showed biphasic curve. The above concentration of ADP, adrenaline and collagen are suitable for the study of platelet aggregation in normal Thai adults.