<prompt> Prothrombin Time PT detects deficiency of all the following clotting factors EXCEPTIIVVIIVIII  <response>: The time required for clotting to occur is called the prothrombin time PT. Normal PT 15-20 seconds. Prolonged PT suggests the possibility of deficiency of factors II prothrombin, V, VII and X. Prothrombin level is low in vitamin K deficiency and various liver and biliary diseases. 