State-of-the-Art Review : Evaluation of the Clot Signature Analyzer as a Hemostasis Test in Healthy Volunteers Exposed to Low Doses of Aspirin

Abstract

Several variables affect bleeding time that make it difficult to obtain consistent 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 bleeding 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 (Surgicutt2) and collagen-induced platelet aggregation, respectively. Fifty-three 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 and then took 243 mg 2 hours later. The changes in each value from the baseline to that at either aspirin dose (2 hours after dosing) were evaluated. Platelet hemostasis time and CITF correlated well with bleeding time and aggregation, respectively, but PHT was not significantly increased after 81 mg of aspirin, whereas bleeding time was significantly increased. The variation in PHT was slightly higher than that of bleeding time. At 81 mg, CITF was significantly increased but aggregation was not, even though the variation 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 conventional method. Also, CITF was more sensitive than aggregation in detecting platelet response to collagen. In conclusion, the proposed CSA is not always suitable for detecting hemostatic abnormalities.

Point-of-Care Assessment of Antiplatelet Agents in the Perioperative Period: A Review

“…The few studies on the sensitivity of the CSA for the detection of antiplatelet drug effects have not been encouraging. Igawa et al found that in 53 normal volunteers, the PHT increased following the ingestion of low doses of aspirin 56 . However, the coefficient of variation for the PHT was very wide (49 to 65%) and the CITF showed little change.…”

Epidural anesthesia prevents hypercoagulation in patients undergoing major orthopedic surgery

“…We therefore decided to use CSA to assess information about platelet function (represented by the parameters, PHT and CITF) and coagulation processes (CT). CSA has been used previously for determination of clinical clotting disorders, [17][18][19] but not in the setting of surgery. To our knowledge, our findings represent the first time a coagulation test was able to demonstrate that orthopedic surgery induces hypercoagulability, and that the use of EA prevents this effect.…”