From the Guidelines
Prothrombin time (PT) or International Normalized Ratio (INR) testing is ordered in stroke patients primarily to guide treatment decisions, especially regarding anticoagulation therapy. When a patient presents with suspected stroke, we need to determine whether it's ischemic or hemorrhagic, as treatment approaches differ dramatically. If the patient is on warfarin or other vitamin K antagonists, the PT/INR helps assess their anticoagulation status, which is crucial because excessive anticoagulation increases hemorrhage risk. For patients with ischemic stroke who might be candidates for thrombolytic therapy with tissue plasminogen activator (tPA), an elevated INR above 1.7 is a contraindication to this treatment, as stated in the guidelines from the American Heart Association/American Stroke Association 1.
Some key points to consider when ordering a PT in a patient suspected of stroke include:
- Determining the patient's coagulation status to guide anticoagulation therapy
- Assessing the risk of hemorrhage in patients on warfarin or other vitamin K antagonists
- Evaluating the safety of initiating antiplatelet or anticoagulant medications for secondary prevention
- Guiding the management of bleeding risk in patients requiring urgent neurosurgical intervention
According to the Canadian Stroke Best Practice Recommendations, updated in 2015, acute blood work, including coagulation studies such as PT/INR, should be conducted as part of the initial evaluation of patients with suspected acute stroke 1. The results of these tests can help identify potential contraindications for thrombolytic therapy and inform decisions about anticoagulation and antiplatelet therapy.
In terms of specific guidelines, the American Heart Association/American Stroke Association recommends that PT/INR be performed in all patients with suspected ischemic stroke, unless there is a clear contraindication 1. The Canadian Stroke Best Practice Recommendations also emphasize the importance of coagulation studies, including PT/INR, in the initial evaluation of patients with suspected acute stroke 1.
Overall, ordering a PT in a patient suspected of stroke is crucial for guiding treatment decisions and ensuring the safe use of anticoagulation and antiplatelet therapy. By assessing the patient's coagulation status and identifying potential contraindications for thrombolytic therapy, healthcare providers can make informed decisions about the best course of treatment for each individual patient.
From the Research
Ordering PROTIME in Suspected Stroke Patients
- The prothrombin time (PT) test is essential in evaluating patients with suspected stroke, particularly those who may be taking anticoagulant medications like warfarin 2, 3, 4.
- An abnormal PT result can indicate hypocoagulability, which may contraindicate the use of intravenous thrombolysis (IVT) in acute ischemic stroke (AIS) patients 2, 4.
- However, studies have shown that IVT can be safely administered to warfarin-treated patients with subtherapeutic international normalized ratio (INR) values 5, 6.
- The PT test can help identify patients who may be at risk of bleeding complications if IVT is administered, allowing for prompt reversal of anticoagulation and minimizing delays in treatment 4.
Indications for PROTIME Testing
- Anticoagulant monitoring is a common indication for ordering PT tests, particularly in patients taking warfarin 3.
- Initial evaluation of hemorrhage and preoperative screening are also indications for PT testing, although the latter is not generally recommended 3.
- In the context of suspected stroke, PT testing can help guide treatment decisions, including the use of IVT and the need for anticoagulation reversal 2, 4, 5, 6.
Interpretation of PROTIME Results
- Prolonged PT results can indicate hypocoagulability, which may be due to various factors, including anticoagulant medication, liver disease, or vitamin K deficiency 3.
- The interpretation of PT results should take into account the patient's clinical context, including their medical history, medication use, and laboratory results 3, 4.
- In patients with suspected stroke, PT results can help inform treatment decisions, including the use of IVT and the need for anticoagulation reversal 2, 4, 5, 6.