Prolongation of the time taken for a standardized skin cut of fixed depth and length to stop bleeding.

An abnormal susceptibility to bleeding, often referred to as a bleeding diathesis. A bleeding diathesis may be related to vascular, platelet and coagulation defects.

An impairment in the rate and degree to which platelets aggregate after the addition of an agonist that stimulates platelet clumping. Platelet aggregation is measured using aggregometer to measure the optical density of platelet-rich plasma, whereby platelet aggregation causes the plasma to become more transparent.

An abnormality of adhesion of thrombocytes. Normally, platelets adhere to collagen in the vascular subendothelium within seconds of injury via a receptor made up of glycoprotein Ia and IIa and GPVI and to vWF via receptor GPIb/IX/V. The adherent platelets then release granules that lead to platelet activation and aggregation.