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A 74-year-old man presented with spontaneous, acute onset of confusion and headache. He had no preceding head trauma or falls. He had a history of atrial fibrillation with an annual stroke risk of 2.9% (based on points accrued for hypertension and age ≥65 years using the CHA2DS2-VASc score1). He was being treated with rivaroxaban, 20 mg daily. He took his last dose 14 hours prior to presentation. Other medications included ramipril and rosuvastatin.
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B. The patient’s hemostatic status is not appropriate for surgery because the abnormal PT suggests anticoagulant effect from rivaroxaban.
Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are clot-based tests that measure the length of time required for thrombus formation in the presence of specific reagents. PT measures the activity of extrinsic (factor VII) and common (factors II, V, X) coagulation pathways and was originally introduced for monitoring vitamin K antagonist therapy (eg, warfarin).2 aPTT measures the activity of intrinsic (factors VIII, IX, XI, and XII) and common coagulation pathways and was developed as a preoperative screen for hemophilia in high-risk individuals, but later validated for monitoring therapy with unfractionated heparin.3
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Corresponding Author: Michelle Sholzberg, MD, MSc, Coagulation Laboratory, St. Michael's Hospital, 30 Bond St, Toronto, ON M5B 1W8, Canada (firstname.lastname@example.org).
Published Online: September 14, 2018. doi:10.1001/jama.2018.13998
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Additional Contributions: We thank the patient for granting permission to publish this information.
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