<prompt> All are to access platelet functions except-Prothrombin timeBleeding timeClot retraction timeProthrombin deactivation  <response>: ROBBINS BASIC PATHOLOGY 9THEDITION PGNO 450 Prothrombin time PT. This test assesses the extrinsic and common coagulation pathways. It measures the time in seconds needed for plasma to clot after addition of tissue thromboplastin e.g., brain extract and Ca2 ions. A prolonged PT can result from a deficiency of factor V, VII, or X or prothrombin or fibrinogen, or by an acquired inhibitor typically an antibody that interferes with the extrinsic pathway. 