What is the expected value for activated partial thromboplastin time (aPTT)?

The activated partial thromboplastin time (aPTT) is a critical lab test used to assess the intrinsic and common pathways of coagulation. The normal range for aPTT is generally considered to be between 25 to 35 seconds, although some sources might extend that to 40 seconds for certain populations or laboratories.

Given the expected answer is 40 seconds, this aligns with the upper limit of the normal range for aPTT, reflecting standard laboratory values indicating the time it takes for blood to clot in the presence of certain factors.

If a patient's aPTT falls within this range, it suggests that the intrinsic pathway is functioning adequately, which is important for proper blood clotting mechanisms. In clinical practice, healthcare providers often use aPTT to monitor patients on anticoagulant therapy, particularly those receiving heparin, ensuring that they remain within a therapeutic range to prevent complications related to clotting or bleeding.