What test is commonly used to check blood clotting time?

The International Normalized Ratio (INR) is a standardized measure for assessing blood clotting time, particularly in patients who are on anticoagulant therapy, such as warfarin. The INR allows clinicians to compare results across different laboratories and testing methods, providing an essential tool for the adjustment of anticoagulant dosage.

The INR is derived from the Prothrombin Time (PT) test, which measures the time it takes for blood to clot. While the PT itself provides valuable information about clotting function, the INR is crucial for ensuring that this information is consistent and reliable, especially for patients needing precise management of their blood coagulation status.

In contrast, while Partial Thromboplastin Time (PTT) also evaluates clotting ability, it focuses on different pathways of the coagulation cascade and is primarily used for assessing the intrinsic pathway of coagulation and monitoring heparin therapy, making it less applicable as a general or standardized test compared to the INR. The Complete Blood Count (CBC) assesses various components of blood, such as red blood cells and white blood cells, but does not specifically measure clotting time directly.