American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the threshold INR for administering tPA in patients with ischemic stroke?

1. 2.0

2. 1.7

3. 1.5

4. 1.0

The correct answer is: 1.7

The threshold INR for administering tissue plasminogen activator (tPA) in patients with ischemic stroke is crucial for ensuring patient safety while maximizing the benefits of thrombolysis. An INR of 1.7 is the recommended threshold, meaning that if a patient has an INR higher than this value, they may have an increased risk of hemorrhagic complications from tPA administration. The rationale behind this specific INR cutoff is to balance the risk of inducing a hemorrhagic stroke against the potential benefits of restoring blood flow to the affected brain area. An INR of 1.7 indicates slight anticoagulation, which is acceptable for tPA but above this level poses significant risks. This threshold is backed by clinical guidelines and studies that have shown that patients with an INR above this level have higher rates of intracranial hemorrhage when treated with tPA. In the context of the other values, while an INR of 2.0 or above would indicate a higher likelihood of complications, lower values such as 1.5 or 1.0 are generally considered safer, but they fall below the recommended threshold used in clinical practice, indicating that tPA may still be safely administered even with slightly higher levels of INR, up to that 1