NIH Module 7 – Laboratory Testing, Diagnostic Imaging, and Screening Practice Test

The concept being tested is identifying what the PT test measures and its normal reference range. PT stands for prothrombin time, a lab test that evaluates the extrinsic pathway of coagulation by timing how long it takes blood to clot after adding tissue factor. A typical normal range is about 11 to 13.5 seconds, though exact values can vary by lab. This reflects normal functioning of the coagulation factors in the extrinsic and common pathways.

Other options describe different things: Partial Thromboplastin Time refers to a different test (PTT) that assesses the intrinsic pathway, with a typical normal range around 25–40 seconds. Platelet count is a measure of platelets per volume of blood, not a clotting time, usually expressed as 150–450 x 10^9/L.