Quiz

Emergency Medicine

Coagulation Test Interpretation in a Patient Taking Direct Oral Anticoagulant Therapy

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.

1 Credit CME

JAMA

October 9, 2018

JAMA Diagnostic Test Interpretation

Article Information and Disclosures

Michelle Sholzberg, MDCM, MSc^1,2,3;

Yan Xu, MD¹

Author Affiliations

¹Department of Medicine, University of Toronto, Toronto, Ontario, Canada
²Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, Canada
³Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada

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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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Article Information

Corresponding Author: Michelle Sholzberg, MD, MSc, Coagulation Laboratory, St. Michael's Hospital, 30 Bond St, Toronto, ON M5B 1W8, Canada (sholzbergm@smh.ca).

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.

References

Lip GY, Lane DA. Stroke prevention in atrial fibrillation: a systematic review. JAMA. 2015;313(19):1950-1962. doi:10.1001/jama.2015.4369 PubMed Google Scholar Crossref

Hylek EM, Go AS, Chang Y, et al. Effect of intensity of oral anticoagulation on stroke severity and mortality in atrial fibrillation. N Engl J Med. 2003;349(11):1019-1026.PubMed Google Scholar Crossref

Kitchens CS. To bleed or not to bleed? is that the question for the PTT? J Thromb Haemost. 2005;3(12):2607-2611. doi:10.1111/j.1538-7836.2005.01552.x PubMed Google Scholar Crossref

Cuker A, Siegal DM, Crowther MA, Garcia DA. Laboratory measurement of the anticoagulant activity of the non-vitamin K oral anticoagulants. J Am Coll Cardiol. 2014;64(11):1128-1139. PubMed Google Scholar Crossref

Jabet A, Stepanian A, Golmard JL, et al. Are screening tests reliable to rule out direct oral anticoagulant plasma levels at various thresholds (30, 50, or 100 ng/mL) in emergency situations? Chest. 2018;153(1):288-290. PubMed Google Scholar Crossref

Tomaselli GF, Mahaffey KW, Cuker A, et al. 2017 ACC Expert Consensus Decision Pathway on Management of Bleeding in Patients on Oral Anticoagulants. J Am Coll Cardiol. 2017;70(24):3042-3067. PubMed Google Scholar Crossref

Heidbuchel H, Verhamme P, Alings M, et al. European Heart Rhythm Association Practical Guide on the use of new oral anticoagulants in patients with non-valvular atrial fibrillation. Europace. 2013;15(5):625-651. PubMed Google Scholar Crossref

Gosselin RC, Adcock DM, Bates SM, et al. International Council for Standardization in Haematology (ICSH) recommendations for laboratory measurement of direct oral anticoagulants. Thromb Haemost. 2018;118(3):437-450.PubMed Google Scholar

Bates SM, Weitz JI. Coagulation assays. Circulation. 2005;112(4):e53-e60. PubMed Google Scholar Crossref

10.

Antovic JP, Skeppholm M, Eintrei J, et al. Evaluation of coagulation assays versus LC-MS/MS for determinations of dabigatran concentrations in plasma. Eur J Clin Pharmacol. 2013;69(11):1875-1881. PubMed Google Scholar Crossref

Coagulation Test Interpretation in a Patient Taking Direct Oral Anticoagulant Therapy

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Coagulation Test Interpretation in a Patient Taking Direct Oral Anticoagulant Therapy

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