Evaluation of the clot signature analyzer as a hemostasis test in healthy volunteers exposed to low doses of aspirin

Several variables affect bleeding time that make it difficult to obtain con sistent measurements. The Clot Signature Analyzer (CSA) has been developed to assess in vitro hemostasis using well-controlled flow chambers. In this study, the equivalencies in the CSA parameters with the conventional bleedi ng time or platelet aggregation methods were evaluated in subjects exposed to aspirin. The CSA parameters, platelet hemostasis time (PHT) and collagen -induced thrombus formation (CITF), were compared to bleeding time (Surgicu tt2(R)) and collagen-induced platelet aggregation, respectively. Fifty-thre e healthy volunteers were given two doses of aspirin (81 and 243 mg) in one day. Following the baseline period, the volunteers took 81 mg of aspirin a nd then took 243 mg 2 hours later. The changes in each value from the basel ine to that at either aspirin dose (2 hours after dosing) were evaluated. P latelet hemostasis time and CITF correlated well with bleeding time and agg regation, respectively, but PHT was not significantly increased after 81 mg of aspirin, whereas bleeding time was significantly increased. The variati on in PHT was slightly higher than that of bleeding time. At 81 mg, CITF wa s significantly increased but aggregation was not, even though the variatio n was comparable. This suggests that PHT and CITF can simulate the changes in bleeding time and aggregation, respectively, but the sensitivity of PHT for detecting the changes in bleeding time was no better than the conventio nal method. Also, CITF was more sensitive than aggregation in detecting pla telet response to collagen. In conclusion, the proposed CSA is not always s uitable for detecting hemostatic abnormalities.