Thromboelastography: a reliable test?

Abstract

The thromboelastograph (TEG), a measure of global haemostasis, is routinely used during cardiac and hepatic surgery to optimize blood product selection and usage. It has recently been suggested that it may also be a useful tool to screen patients with hypercoagulable states. Limited published data on performance characteristics has led to speculation regarding its consistency and, therefore, validity of the results. This study was designed to assess the effect of stability of blood samples prior to testing, repeated sampling, intra- and inter-assay variability using the native, celite, tissue factor (TF) and Reopro-modified TEG. Analysis of native and celite samples after storage over 90 min showed a period of instability up to 30 min. Thereafter, all parameters between 30 and 90 min were stable [P = not significant (NS)]. When the same sample was repeatedly assayed, both native and celite TEG parameters showed a significant change towards hypercoagulability (P < 0.01), whereas the TF and Reopro-modified TEG showed no change. Intra- and inter-assay variability on samples tested after 30 min showed excellent reproducibility for all parameters (P = NS). The data suggest that the TEG is a useful tool in haemostasis but requires a formal standard operating procedure to be adopted that takes into account the initial period of sample instability.

Technical report: Analysis of citrated blood with thromboelastography: comparison with fresh blood samples

“…[7][8][9][10] Another concern is that the storage time of citrated blood samples may influence TEG measures. [7][8][9]11 Consequently, to compare the results of TEG analysis, performed on non citrated blood, analyzed within five minutes of collection, with the values of citrated blood, stored, with and without use of activators, for one to three hours, we carried out this observational study on healthy volunteers.…”

“…Another explanation is the possibility that transferring a blood sample from the syringe to the TEG cup may result in contact activation. 11 The reason that a hypercoagulable tendency was not observed in kaolin activated samples is unclear. Nevertheless, these findings suggest that TEG measures on citrated blood samples should be performed with kaolin, rather than with TF activation.…”

“…Firstly, the study cohort consisted of ten, healthy volunteers. Based on previous studies of TEG on volunteers, 7,8,11 we anticipated that this sample size would provide a precise estimate of the distribution of TEG measures. The sample size, however, was too small to allow us to analyze gender effects on TEG measurements.…”

“…Secondly, because we recruited healthy volunteers, our findings may not be applicable to patients with congenital or acquired coagulation defects, where TEG measure distributions are likely to be more variable and abnormal. 11 Finally, we did not perform TEG analyses with citrated samples during the first hour of storage and, consequently, we cannot comment on sample stability during this time. Previous studies have found that citrated samples produce unstable results during the first 30 min of storage.…”

“…Previous studies have found that citrated samples produce unstable results during the first 30 min of storage. 9,11 FIGURE 5 Thromboelastogram results of maximum amplitude (time = 0) and citrated blood at one, two, and three hours after storage. Blood samples were analyzed without activation (<, native), with tissue factor (TF) activation (5, TF), and with kaolin activation (♦, kaolin).…”