Thrombin generation testing in routine clinical practice: are we there yet?

Abstract

Summary Thrombin is the central enzyme in the coagulation cascade. Estimation of an individual’s potential to generate thrombin may correlate more closely with a hyper‐ or hypo‐coagulable phenotype, compared to traditional coagulation tests. The possible correlation and recent technical advances in thrombin generation measurement has caused a significant interest in the method and the development of commercial assays. Several variations of the assay exist depending on the defect to be investigated. Fluorogenic thrombin generation assays have acceptable intra‐laboratory variation but a higher inter‐laboratory variation. Variation in preanalytical variables makes comparisons between studies difficult. Thrombin generation is highly variable between individuals and there are suggestions that this may allow individualized treatment based on global haemostatic response in patients with bleeding disorders or on anticoagulant therapy. In patients with thrombotic disorders it may be possible to identify those at higher risk of recurrent thrombosis. For both scenarios, however, data from large prospective studies are lacking or inconclusive and a good relationship between thrombin generation and phenotype remains to be established. Further standardization of the assay is needed before large multicentre studies can be conducted and until then thrombin generation in routine clinical practice is not yet a reality.

Large inter-individual variation of the pharmacodynamic effect of anticoagulant drugs on thrombin generation

“…We start from the a priori assumption -supported by a wealth of literature 16,20,[24][25][26][27][28][29][30] -that thrombin generation is a sensitive surrogate variable for bleeding or, conversely, thrombotic tendency. All known drugs that diminish thrombin generation have an antithrombotic action, independently of their mode of action.…”

A review of commercially available thrombin generation assays

“…Using a mathematical calculation known as an H‐transform, it is possible to take the acquired data and to generate a diagnostic plot that accounts for the inner filter effect and the substrate consumption 14. However, even with this correction there can also be quenching from various compounds in the plasma that can change from sample to sample and can in turn affect the results of the plot 15. For the Technothrombin system there is no correction for this inner filter effect, resulting in a lower overall ETP and shorter peak height versus that of the Thombinoscope which does factor the inner filter effect into the calculations 16.…”

“…In the case of the BCS method the results are provided as milliabsorption units (mA), based on the absorbance of the chromophore. The same parameters are determined by the two fluorogenic assays, except the results are expressed in nanomolar thrombin, since the use of an internal standard allows for conversion of fluorescence to the corresponding concentration of thrombin 15. Both the CAT and BCS methods measure the thrombogram over the course of minutes though the BCS often reports its data in seconds rather than minutes.…”

“…Ten Huge and van Veen et al. have studied thrombin generation and found that while useful for many disorders such as venous thrombosis, arterial disease, and various bleeding disorders, there is a significant issue with standardization between centers 15, 30. Tripodi points out that while automated thrombography has helped in elucidating the clotting mechanism to many diseases that were previously unknown, there have been insufficient studies of the clinical use of these assays 31.…”

Thrombin generation in patients with a bleeding tendency of unknown origin

“…The accumulation of thrombin at sites of vascular injury provides an important mechanism for the gathering of platelets and the formation of a growing haemostatic plug. Recent advances in laboratory technologies gave rise to the development of new assays to measure the in-vitro thrombin generation, which reflects the overall coagulation potential [3][4][5][6].…”