EFFECT OF DELAY AND STORAGE ON WHOLE BLOOD CLOTTING ANALYSIS AS DETERMINED BY THROMBELASTOGRAPHY

The thrombelastogram (TEG) measures the viscoelastic properties of clotting blood, displaying a visual trace of all phases of coagulation and fibrinolysis. Thrombelastography can be performed on whole blood (WBTEG) or on citrated blood or plasma, citrated samples facilitating delayed analysis but requiring recalcification of the sample. The aim of this study was to investigate the effect of delay and storage method on WBTEG measurement. Thrombelastographic analysis of coagulation in whole blood was investigated after delays of 3 and 6 minutes in polystyrene syringes (PS3 and PS6) and 3 minutes in silicone-coated glass tubes (SG3). Thrombleastograms of the delayed samples were compared with those measured immediately. Silicone-coated glass tubes activated coagulation, as seen by shorter r times (p<0.01), shorter r+k times (p<0.01), and larger maximum amplitude (ma) values (p<0.01) compared with TEG values determined immediately after sampling. In the SG3 group, 20% of samples had clotted by 3 minutes, and the use of SG tubes for this purpose cannot be recommended. A delay of 6 minutes in PS had less effect on the activation of clotting in the earlier stages in that the r time was prolonged (p<0.01). However, there appeared to be some activation later in that k time was shorter (p<0.01) and ma was wider (p<0.05). Overall, a 3-minute delay in PS produced the best values. The mean delayed r+k times were 12.6 (SD 2.2) minutes versus mean immediate values of 12.3 (SD 2.1) minutes (difference not significant), while the mean delayed ma was 48.5 (SD 7.3) mm versus the mean immediate value of 47.4 (SD 7.3) mm (difference not significant). A 3-minute delay in PS increases the allowable patient-machine distance and thus increases the number of patient areas where whole blood TEG analysis can be used.