Coagulation is a complex function depending on multiple things.
Bleeding time measures the time taken for a standardized skin puncture to stop bleeding. It assesses platelet response to limited vascular injury. The reference depends on the specific test and varies from 2-9 minutes.
Platelet counts are usually done using an automated counter using anticoagulated blood. Readings well outside the reference range - 130 to 300 x 109/L - need to be verified manually to ensure artifactual clumping hasn't occurred.
Prothrombin time measures the extrinsic and common coagulation pathways. Clotting of plasma is induced by addition of tissue thromboplastin and calcium ions, and is measured in seconds.
Prolonged PT can result from deficiency/dysfunction of factor V, factor VII, factor X, prothrombin, or fibrinogen. PT is also used as a test of liver function
Partial Thromboplastim Time is a measure of intrinsic and common clotting pathways. Plasma clotting after addition of kaolin, cephalin, and calcium ions is measured in seconds.
Prolonged PTT can be due to problems with factor V, VIII, IX, X, XI, or XII, prothrombin, or fibrinogen.
Dade PTT