When should you obtain coagulation tests in the emergency department?

Authors: Umbreen Iftekhar, M.S. PA-C, Minela Subasic, M.S. PA-C, Elizabeth Wallach, M.S. PA-C, Anthony Scoccimarro, MD, and Muhammad Waseem, MD, MS (Lincoln Medical & Mental Health Center, Bronx, New York) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit)

In the Emergency Department, routine use of coagulation order sets or “coags’ include PTT and PT/INR. Unnecessary use of these tests adds to overall healthcare costs. Preoperative evaluation utilizing these laboratory tests is not driven by evidence-based guidelines and not determined by disease characteristics.

 

Routine Pre-operative Screening

Baseline PT and PTT values are routinely obtained despite the fact that they do not alter management or serve as sensitive or specific screening tests.[1] There is not enough evidence to conclude that abnormal test results predict bleeding. Therefore one should not assume that slight elevation of INR or prolongation of PT is predictive of procedural bleeding.[2] In a recent retrospective study that analyzed approximately 1 million pre-operative patients, 26.2% of patients had PT testing of which 94.3% were unnecessary, and 23.3% had aPTT testing, of which 99.9% were unnecessary.[3]

 

Is routine testing for PT/INR and PTT in patients with suspected coronary ischemia necessary?

PT/INR and PTT are often included in the routine evaluation of the chest pain order set. The rationale for obtaining such tests includes the possibility of treating patients with anticoagulants or thrombolysis. They are also employed as screening tests for unrecognized bleeding disorders or hypercoagulable states. Studies suggest that the incidence of significant abnormalities of coagulation laboratory results was low and could have been predicted by either history or physical examination. In addition, the unpredicted abnormalities were minor and had no clinical significance in patient management.[4] The patient history is often the best predictor for bleeding, via a patient’s own reported history of bleeding with prior procedures.

 

Do patients on low molecular-weight heparin (LMWH) require routine PT/INR or PTT monitoring?

The current evidence does not support the use of laboratory monitoring to improve the efficacy of LMWH.[5] Although opinions differ among researchers, it is believed that unless there is a standardized and reproducible method of aXa measurement that can be used by all laboratories performing the aXa assay, monitoring of the therapeutic range of LMWH is not required.[6]

 

What about patients taking novel oral anticoagulants (NOACs)?

Standard PT/INR and PTT testing does not correlate well to determine therapeutic levels of NOACs, including direct thrombin inhibitors (dabigatran) and anti-Xa inhibitors (rivaroxaban and apixaban).  However, in cases of bleeding, a normal aPTT suggests dabigatran is unlikely to contribute. Likewise, a normal PT suggests an anti-Xa inhibitor is unlikely to contribute to bleeding.[7]

 

What you can do to reduce “coags” tests?

Develop Clear Guidelines: It is important to institute clear guidelines to promote the appropriate use of PT and PTT tests in the emergency department.

Develop a Consensus: Discuss the subject in a combined EM, surgical, and anesthesia services meeting. This may be helpful in order to achieve a consensus; otherwise other services may demand “coags” as routine testing.

Before ordering “coags,” consider whether the result will alter or change the management plan.

Consider ordering PT/INR and PTT separately, as each has a different indication.

Use PTT for monitoring heparin, not for determining the initial dosing.

 

When to obtain “coags”?[8],[9]

PT/INR

-Warfarin therapy

-Liver failure

-Vitamin K deficiency

 

PTT

-Heparin treatment

-Hemophilia

-von Willebrand disease

 

Both (PT/INR and PTT)

-Bleeding of unknown etiology

-Bleeding by history or presence of bleeding

-Known or suspected coagulopathy (e.g. disseminated intravascular coagulation)

-History cannot be obtained or unreliable history

 

Ask yourself these questions before ordering PT/PTT:

-Does this patient have a history of bleeding or, on examination, is the patient bleeding?

-Is this patient taking warfarin?

-Does this patient have a history of liver disease, von Willebrand disease, or lupus anticoagulant antibodies?

 

References / Further Reading:

[1] McKinley L, Wrenn K. Are baseline prothrombin time/partial thromboplastin time values necessary before instituting anticoagulation? Ann Emerg Med. 1993;22:697-702.

[2] Segal JB, Dzik WH; Transfusion Medicine/Hemostasis Clinical Trials Network. Paucity of studies to support that abnormal coagulation test results predict bleeding in the setting of invasive procedures: an evidence-based review. Transfusion. 2005 Sep;45(9):1413-1425

[3] Capoor, Manu N., et al. “Prothrombin time and activated partial thromboplastin time testing: a comparative effectiveness study in a million-patient sample.” PloS one 10.8 (2015): e0133317.

[4] Schwartz D. Utility of routine coagulation studies in emergency department patients with suspected acute coronary syndromes. Isr Med Assoc J. 2005 Aug;7(8):502-506

[5] Bounameaux H, de Moerloose P. Is laboratory monitoring of low-molecular-weight heparin therapy necessary? No. J Thromb Haemost. 2004 Apr;2(4):551-554

[6] Shojania AM. More on: Is laboratory monitoring of low-molecular-weight heparin necessary? J Thromb Haemost. 2004 Dec;2(12):2276-7

[7] Cushman, M., W. Lim, and N. A. Zakai. “Clinical practice guide on antithrombotic drug dosing and management of antithrombotic drug-associated bleeding complications in adults.” (2014).

[8] Lin M., Schuur J. What Emergency Physicians Can Do to Reduce Unnecessary Coagulation Testing in Patients with Chest Pain. ACEP Now. May 2014  Available at http://www.acepnow.com/article/emergency-physicians-can-reduce-unnecessary-coagulation-testing-patients-chest-pain/

[9] Karas SJ, Cantrill SV, eds. Cost-Effective Diagnostic Testing in Emergency Medicine: Guidelines for Appropriate Utilization of Clinical Laboratory and Radiology Studies. 2nd ed. Dallas, Tex: American College of Emergency Physicians; 2000.

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