Abstract: Objective To evaluate turbidity measurement which is used to study the variability and variation amplitude of platelet aggregation and its application. Methods LBY-NJ4 aggregometer was use to test coefficients of variation (CV) of different inducers which induce platelet aggregation, evaluate the effect and variability of aspirin and panax notoginseng (PNs) inhibition of platelet aggregation. Results With adenosine diphosphate (ADP) and collagen, the CV of maximum aggregation rate, aggregation rate and area under the curve were less than 4%, 4% and 7% respectively, while with thrombin the CV of aggregation rate was larger(24.45%). Washed platelet was engaged to the aggregation of thrombin to remove the effect of fibrin, the CV of aggregation rate was reduced to 4.42%. PNs inhibited thrombin-induced platelet aggregation with a dose-depend manner, the CVs of three parameters were ranged from 1.58% to 12.34%, more stable than that of aspirin. Conclusion Turbidity measurement can be used to test platelet aggregation, three parameters are stable and useful for the evaluation of traditional Chinese medicine for huoxuehuayu.

Key words: turbidity measurement, platelet aggregation, coefficient of variation