<unk>  (F1+2), also written as<unk>  (F1.2), is a polypeptide<unk>  of<unk>  (factor II) generated by the in vivo cleavage of<unk>  into thrombin (factor IIa) by the enzyme<unk> ase (a complex of factor Xa and factor Va). It is released from the N-terminus of<unk> . F1+2 is a marker of thrombin generation and hence of coagulation activation. It is considered the best marker of in vivo thrombin generation. F1+2 levels can be quantified with blood tests and is used in the diagnosis of hyper- and hypocoagulable states and in the monitoring of anticoagulant therapy. It was initially determined with a radioimmunoassay, but is now measured with several enzyme-linked immunosorbent assays. The molecular weight of F1+2 is around 41 to 43 kDa. Its biological half-life is 90 minutes and it persists in blood for a few hours after formation. The half-life of F1+2 is relatively long, which makes it more reliable for measuring ongoing coagulation than other markers like thrombin–antithrombin complexes and fibrinopeptide A. Concentrations of F1+2 in healthy individuals range from 0.44 to<unk> .11 nM. F1+2 levels increase with age. Levels of F1+2 have been reported to be elevated in venous thromboembolism, protein C deficiency, protein S deficiency, atrial fibrillation, unstable angina, acute myocardial infarction, acute stroke, atherosclerosis, peripheral arterial disease, and in smokers. Anticoagulants have been found to reduce F1+2 levels. F1+2 levels are increased with pregnancy and by ethinylestradiol-containing birth control pills. Conversely, they do not appear to be increased with estetrol- or estradiol-containing birth control pills. However, F1+2 levels have been reported to be increased with oral estrogen-based menopausal hormone therapy, whereas transdermal estradiol-based menpausal hormone therapy appears to result in less or no consistent increase.
Prothrombin fragment 1+2
Factor VIII
Factor VIII 
Β-Thromboglobulin
Factor IX
Fibrinogen
Von Willebrand factor
Fibrinogen beta chain