Development and validation of a new assay for assessing clot integrity

Research and routine laboratory assessment of clot integrity can be time consuming, expensive, and cannot be batched as it is generally performed in real time. To address these issues, we developed and validated a micro-titre based assay to quantify thrombogenesis and fibrinolysis, the purpose being to assess patients at risk of cardiovascular events by virtue of hypercoagulability. In further validation, thrombogenesis results were compared to similar indices from the thrombelastograph (TEG).

Our assay determines three indices of thrombogenesis (lag time to the start of thrombus formation (LT), rate of clot formation (RCF), and maximum clot density (MCD)) and two of fibrinolysis (rate of clot dissolution (RCD) and time for 50% of the clot to lyse (T50)). Plasma was tested fresh and again after being frozen at -70°C. Some samples were tested immediately, others after being left at room temperature for up to 24h.

The intra-assay coefficients of variation (CVs) of the three thrombogenesis measures (LT, RCF, MCD) and two fibrinolysis measures (RCD, T50) varied between 2.7 and 12.0% in fresh plasma and between 1.3% and 10.8% in frozen plasma respectively. Similarly, the inter-assay coefficients of variation of the thrombogenesis and fibrinolysis measures were 4.9-10.8% in fresh plasma and 2.2-6.5% in frozen plasma respectively. TEG assays intra- and inter assay CVs were around 25%. There were no significant differences in all plate assay indices up to 6h at room temperature. Certain plate assay thrombogenesis data were comparable to TEG indices after analysis by Pearson's correlation. The reagent processing cost per sample is £15 for TEG and £2 for the plate assays.

Our micro-titre based assay assessing plasma thrombogenesis and fibrinolysis has good intra- and inter-assay CVs, can assess plasma up to 6h after venepuncture, is more efficient (in terms of throughput) and is more economical than that of the TEG.