Assessment of hypercoagulable states by measurement of activation fragments and peptides

Broad spectrum assays which measure a range of fibrinogen/fibrin derivatives (FDPs) in serum have become an established means of identifying activation of blood coagulation and/or fibrinolysis, such as occurs in disseminated intravascular coagulation (DIC). There is considerable interest in the application of these assays to the diagnosis of other hypercoagulable states, such as recurrent deep venous thrombosis and myocardial infarction. In recent years, more sensitive and specific FDP assays (e.g. for fragment E, fragment E neoantigen, D-dimer, fragment D neoantigen, fibrinopeptide A and fibrin fragment beta 15-42) have been devised, some of which allow measurement in plasma of FDPs without interference from fibrinogen or certain of its derivatives. It was predicted that these assays would both avoid the possibility of artifacts introduced as a consequence of serum preparation and improve detection of hypercoagulable states. In the light of these expectations we have reviewed data published on the use of assays to detect clinical hypercoagulability, giving prominence to assays of crosslinked fibrin derivatives and nothing particularly certain studies that have compared the performance of different assays on the same samples. The accumulating evidence indicates that all of the assays are adequate for detection of DIC. The same cannot be said for other hypercoagulable states. Here much variation is evident between different studies of similar patients in the ability of a particular marker to discriminate between a normal control group and patients determined to be hypercoagulable by an independent method. This variability would seem to be a function of patient group heterogeneity and selection, as assays that detect different antigenic determinants produce results on the same plasma samples that are well correlated. It appears that the precise antigenic determinant does not critically affect detection of hypercoagulability. Additionally, some studies have indicated that use of serum need not introduce artifacts. Despite there being no other obvious advantage, the convenience of some of the plasma assays may well encourage their widespread use. Assays have also been developed for measuring activation fragments of coagulation proteins (e.g. prothrombin fragment F1 + 2 and protein C activation peptide) and for proteinase inhibitor complexes (e.g. thrombin-antithrombin complex) generated during activation of coagulation. The latter assays have been useful in providing a biochemical definition of a 'prethrombotic state'.