Impact of incorrect filling of citrate blood sampling tubes on thromboelastometry.

BACKGROUND: ROTEM(®) test results can be affected by the citrate to blood ratio in the tested sample. Overfilling or underfilling specimen tubes can change this ratio.

OBJECTIVES: The aim of this study was to determine the impact of under- and overfilling citrate test tubes on ROTEM(®) EXTEM measurements.

RESULTS: Overall repeated measures ANOVA demonstrated significant differences of CT (p = 0.004), CFT (p = 0.005), A5 (p = 0.001), A10 (p <0.001), and MCF (p < 0.001). Pairwise comparison revealed that underfilling significantly altered the results of those parameters reflecting functional clot firmness (A5, A10, and MCF), while overfilling led to a prolongation of the CT results only. No differences were observed for alpha angle and maximum lysis.

CONCLUSION: Both underfilling and overfilling specimen tubes have significant influence on the results of the ROTEM(®) EXTEM test, although the small observed bias is likely of limited clinical relevance. However, it seems prudent to limit the maximum allowed difference in filling to less than ± 10%. All ROTEM(®) operators should be aware of this pre-analytical variable.