Among patients who have undergone orthopedic surgery, a novel clot waveform analysis (CWA)-small amount tissue factor-induced clotting factor IX (FIX) assay appears to effectively detect hemostatic abnormalities, according to research published in Clinical and Applied Thrombosis/Hemostasis.

Patients who undergo major orthopedic surgery, including total hip arthroplasty and total knee arthroplasty, have a high risk of venous thromboembolism (VTE), which may be fatal if undetected and left untreated. Many patients who undergo such surgery are treated with prophylactic low molecular weight heparin or direct oral anticoagulants.

While these drugs can be effective for preventing VTE, some patients must discontinue therapy because of bleeding events. This necessitates effective vigilance against such events, which requires effective monitoring of activated partial thromboplastin time (APTT) and prothrombin time.

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Previous research suggested that CWA of APTT (APTT-CWA) may be effective for detecting disseminated intravascular coagulation and measuring factor VIII levels, both of which are relevant in bleeding events. Other research suggests, however, that routine assays, including APTT-CWA, may not be able to effectively measure FIX activation (FIXa).

For this study, researchers evaluated whether a small amount of tissue factor (sTF)-induced FIX activation assay in platelet-rich plasma using CWA (CWA-sTF/FIXa) yielded superior results to those of a CWA-APTT in platelet-poor plasma. The results were evaluated using data from patients who underwent major orthopedic surgery who were treated with edoxaban.

Overall, data from 147 patients who underwent total hip arthroplasty (109 patients) or total knee arthroplasty (38 patients) were included. A total of 21 patients had a deep vein thrombosis and 15 had a massive bleeding event.

Analysis showed that peak CWA-sTF/FIX heights occurred in most patients after surgery, including the majority of patients who were treated with edoxaban. Peak CWA-sTF/FIX heights/times were both significantly higher and significantly shorter in platelet-rich plasma than in platelet-poor plasma.

CWA-sTF/FIXa heights and times did not differ between those with/without deep vein thrombosis or between patients with/without massive bleeding events. CWA-sTF/FIX also detected hemostatic abnormalities post-surgery and after edoxaban administration; the results were better in platelet-rich plasma.

“In conclusion, the CWA-sTF/FIXa using [platelet-rich plasma] is useful for evaluating hemostatic abnormalities after surgery and the administration edoxaban,” the authors wrote in their report. “Further study should be separately analyzed in [total hip arthroplasty] and [total knee arthroplasty] subgroups.”


Hasegawa M, Tone S, Wada H, et al. The evaluation of hemostatic abnormalities using a CWA-small amount tissue factor induced FIX activation assay in major orthopedic surgery patients. Clin Appl Thromb Hemost. 2021;27:10760296211012094. doi:10.1177/10760296211012094