Rotation thromboelastometry (ROTEM®) stability and reproducibility over time

Background: Thromboelastometry is a whole blood assay performed to evaluate the viscoelastic properties during blood clot formation and lysis. Rotation thromboelastography (ROTEM®, Pentapharm GmbH, Munich, Germany) has overcome some of the limitations of classic thromboelastography. So far, no clinical validation on reproducibility (inter- and intra-assay variability) and sample stability over time has been published. Methods: To evaluate the pre-analytic aspects, sample stability over time was assessed in 48 patients in eight age groups. Citrated blood was stored at room temperature. Tests measured every 30min from T 0min up to T 120min on two ROTEM® devices were INTEM (ellagic acid activated intrinsic pathway), EXTEM (tissue factor-triggered extrinsic pathway) and FIBTEM (with platelet inhibitor (cytochalasin D) evaluating the contribution of fibrinogen to clot formation). Precision by intra- and inter-assay variability was evaluated at two points of time in 10 volunteers. Finally, reference intervals and effect of age and sex were evaluated. Results: Blood was stable over 120min and no significant differences in ROTEM® results were found. Maximum clot firmness measurements had a coefficient of variation of ≪3% for EXTEM, ≪5% for INTEM and ≪6% for FIBTEM. For clot formation time, the coefficient of variation was ≪4% for EXTEM and ≪3% for INTEM. Coefficient of variation for angle alpha was ≪3% for EXTEM and ≪6% for INTEM. The coefficient of variation for clotting time was ≪15% for both EXTEM and INTEM. Small but significant differences between ROTEM® devices were found for maximum clot firmness in FIBTEM and INTEM as well as clot formation time and alpha angle in INTEM. Conclusions: ROTEM® yields stable results over 120min with a minimal variability on the same ROTEM® device. However, small but significant differences between ROTEM® devices were observed. Analysis should be performed on the same ROTEM® device if small differences are of importance for treatmen