Instability of the non-activated rotational thromboelastometry assay (NATEM) in citrate stored blood.

Introduction: The non-activated rotational thromboelastometric assay (NATEM) is increasingly used as sensitive test for the evaluation of the endogenous activation of haemostasis. The reproducibility of the test results in citrate stored blood has never been investigated.

Materials And Methods: The NATEM assay was performed in citrated blood samples stored for 0, 45 and 90minutes using ROTEM® (TEM International, Munich, Germany). Blood samples were drawn from healthy volunteers and a population of patients admitted to the intensive care (ICU). In 10 ICU patients, citrate concentrations were measured at baseline and after 90minutes of storage.

Results: The NATEM clotting time shortened in stored citrated blood from healthy volunteers (t=0 1226±160; t=45 986±171; t=90 903±177; p<0.001) and ICU patients (t=0 986±318; t=90 750±187; p<0.001). A similar decrease in clot formation time (CFT) was seen whereas the MCF remained unaffected. Citrate concentration did not change over time, baseline 13.3±0.5mmol/l; after 90minutes 13.2±0.7mmol/l; n.s..

Conclusions: The non-activated rotational thromboelastometric assay test results change over time in citrate stored blood. The NATEM test should be initiated at a standardised time point, in order to prevent bias by different test initiation times, preferably directly after blood withdrawal.