Basic concept for evaluating coagulation and fibrinolysis data.

"Fibrin is insoluble in blood" is the most important concept to accept the coagulation system. Essentially, blood coagulation is a process to convert blood from soluble to insoluble. Fibrinolysis is another process to convert insoluble protein to soluble protein again. The blood coagulation cascade requires calcium ion and efficiently acts on platelet phospholipid membranes. On the other hand, the fibrinolysis system efficiently acts on fibrin. Unlike other vitamin K-dependent coagulation factors, thrombin can be released from the coagulation site to the systemic circulation and has multiple biological effects regulated through thrombin receptors. Thrombin is captured by thrombomodulin on endothelial cells or anti-thrombin. Low level of coagulation and fibrinolysis idling are always working even under healthy conditions because of shear stress on injured vessels. Measurement of coagulation times, such as PT and APTT, is the basic method used by numerous clinics in coagulation-related examinations. Measurement of coagulation factor activity by one method is based on the concept that excess amounts of coagulation factors circulate in the blood. Under DIC conditions, excess pathological protease activity yields a huge amount of peptides in the blood in addition to coagulation and fibrinolysis markers.