IMPACT Collagen reagent is used to detect platelet dysfunction, or normal platelet activity in whole blood.

Collagen is a structural protein which is virtually ubiquitous throughout the human body. During primary haemostasis following blood vessel injury, the adhesion of platelets to exposed collagen at the site of injury plays a key role in the arrest of bleeding from this site. Any interference with the ability of platelets to interact with exposed collagen is therefore a possible cause of an unexplained bleeding tendency. Some congenital defects of platelet function, as well as some acquired, and drug-induced effects can affect the aggregation of platelets stimulated by collagen.

The test can be affected by aspirin.