Comparison of three independent methods as estimates of platelet inhibition after a single dose of acetylsalicylic acid

Abstract

Karlberg C, Chen J, Egberg N, Nowak J, Sylvén C. Comparison of three independent methods as estimates of platelet inhibition after a single dose of acetylsalicylic acid. Scand J Clin Lab Invest 1993; 53: 835-841.

In order to assess the ability of three different (one in vivo, one ex vivo and one in vitro) methods to estimate platelet function, 10 healthy volunteers were given a single oral dose of 160mg ASA. Platelet function was assessed before, 4, 24, 48 and 72 h after dosing by urinary excretion of thromboxane B₂, filtragometry and collagen-based whole blood aggregometry. Further, in order to study mechanisms for platelet aggregation in filtragometry, platelet activation was assessed by measurements of β-thromboglobulin at three different places within the filtragometer test unit in another nine healthy subjects. Four hours after ASA, the aggregation time during filtragometry increased by 213 ± 133% (p < 0.001) and was parallelled by a decrease in impedance 85 ± 7% (p < 0.001) indicating an inhibition of platelet aggregability in both tests. A subsequent gradual recovery was observed with both methods. The excretion of thromboxane B₂ followed the aggregability pattern being maximally reduced by 72 ± 6% (p < 0.01) 24 h after ASA and then gradually recovering. All three methods indicated that platelet function was still decreased 72 h after dosing. The urinary excretion of prostacyclin did not change significantly. The results of filtragometry and impedance aggregometry correlated to the logarithm of thromboxane B₂ excretion (r = 0.60; p < 0.01 and r = 0.49; p < 0.01, respectively) and to each other (r = 0.70; p < 0.001). In filtragometry β-thromboglobuhn increased significantly (p < 0.05) over the filter. Hence, with a design where inhibition of thromboxane formation alone accounts for the reduction in platelet aggregation, all three methods employed are comparable in estimating platelet function. Also, in filtragometry, platelet activation at the filter seems to contribute to the trapping of platelet aggregates at the filter.

Key Words:

• acetylsalicylic acid
• Aggregation
• Methodology
• Platelets
• thromboxane