The clinical utility of thrombin generation

Abstract

The Calibrated Automated Thrombogram (CAT) thrombin generation assay is a technique that allows the characterisation of an individual’s capacity to produce thrombin in response to a procoagulant stimulus. As such it is a global screening test for both hyper and hypocoagulable bleeding disorders. This project focused on the introduction of the CAT assay into routine use in the haemostasis laboratory at the Royal London hospital and to assess its clinical utility. Initial experimentation focused on determining the suitability of the assay for routine use, including ascertaining the levels of inter and intra assay variation, the effects of sample handling and storage, the limits of detection, variation in an individual with time and establishing a normal range. All of these experiments returned favourable results. The assay was then used to characterise the thrombin generation profile of a cohort of women with pre-eclampsia. Women with pre-eclampsia were found to have higher thrombin generation parameters (Endogenous thrombin potential and peak height) when compared to normotensive pregnant women (p= <0.001). Re-analysis of the data showed the use of thrombin generation could detect pre-eclampsia with a specificity and sensitivity of 83% and 43% respectively when combined with the Pre-eclampsia community guideline screen. There were also statistically significant correlations between the measurement of thrombin generation and both birth weight and the length of stay in hospital at delivery. Further analysis by flow cytometry and studies involving filtration of plasma revealed that the sensitivity of the assay to the detection of pre-eclampsia may be associated with the increased levels of microparticles present in the blood of pre-eclamptic women. There were statistically significant correlations (p= <0.05) between changes in thrombin generation parameters and the number of microparticles post filtration. This suggests that the CAT assay is sensitive to the number of microparticles in a patient’s plasma.