Background: Thrombin generation (TG) is used to measure the overall coagulation potential of a person and to detect hypocoagulability and hypercoagulability. In practice, the assay is also used on an individual level to monitor the effect of anticoagulant treatment or to predict the effect of a drug on haemostasis.

Aims: The goal of this study was to investigate a possible effect of freezing of plasma on TG.

Methods: Platelet poor plasma was obtained from 25 healthy donors after double centrifugation of their citrated blood tubes. TG was measured either in fresh plasma, plasma stored at -20°C or stored at -80°C.  We measured TG on the ST Genesia with three different reagents: STG-BleedScreen (low tissue factor (TF)), STG-ThromboScreen +/- thrombomodulin (medium TF) and STG-DrugScreen (high TF). Samples were tested fresh and after storage at -20°C and -80°C for 1 day. Wilcoxon matched-pairs signed rank test was used for statistical analysis.

Results: Overall, freezing of plasma samples caused an increased TG displayed in a significantly higher peak height (mean increase ±SD; 28.7% ±18.3%) and endogenous thrombin potential (ETP; 36.1% ±25.2%), and a significantly shorter lagtime (-10.5% ±3.4; p-values were all <0.05). This observation was independent of the trigger used and the storage temperature. ETP inhibition by thrombomodulin decreased significantly after freezing, independently of the storage temperature (-31.4% ±3.5%). The procoagulant effect on velocity index and time-to-peak differed in significance between storage temperatures.

Conclusions: Freezing plasma samples either at -20°C or -80°C affects TG significantly compared to fresh samples. Therefore results can only be compared when TG is measured in samples that are equally stored.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/thrombin-generation-is-affected-by-freezing-independent-of-storage-temperature/