What is the primary test used to assess a patient's response to Coumadin?

The primary test used to assess a patient’s response to Coumadin, which is an anticoagulant, is the International Normalized Ratio (INR) test. This test is specifically designed to monitor the effectiveness of Coumadin therapy and ensure that blood coagulation remains within therapeutic ranges to prevent complications such as thrombosis or bleeding.

While the Prothrombin Time (PT) test measures the time it takes for blood to clot and is used in conjunction with the INR for monitoring Coumadin, the INR is the standardized value that accounts for variations in lab testing. Therefore, while PT may be useful, the INR is the preferred method for accurately assessing how well the Coumadin is working in an individual patient and adjusts the treatment based on those results.

The Partial Thromboplastin Time (PTT) test is typically used to monitor unfractionated heparin therapy rather than Coumadin, while a complete blood count (CBC) provides information on various components of the blood but does not offer insight into anticoagulation status. Thus, the INR is the critical measure that informs the clinician about the patient's anticoagulation level while on Coumadin therapy.