TEG and ROTEM: What is the potential for improving patient blood management?
If you’re a frequent reader of this blog, it’s likely that you’ve already made the commitment to embrace the principles of patient blood management (PBM), a laudable decision to be a responsible steward of a precious resource, a champion for improving patient care and clinical outcomes, and a forward-thinking user of data and evidence to drive complex clinical processes.There are many tools that are available to help achieve these goals: data analytics to assist in assessing your performance and charting progress; educational resources to disseminate knowledge about the principles and practices of PBM across your institution; and proven methods for developing the infrastructure to successfully enact these programs on an appropriate scale for your purposes. These resources may be everything you need to effectively achieve your PBM goals, and have certainly helped many institutions promote the kinds of culture changes necessary to be successful. It is not uncommon, though that a successful PBM program inspires an institution to go even further, and seek out new and innovative ways to tailor its transfusion practices to even more closely meet the needs of its patients.
The enthusiasm for continued improvement begs the question: What additional tools are available that can advance the progress that is already being made toward PBM? The experience of many institutions that have made this step, as well as a multitude of publications in the medical literature, suggests that viscoelastic (VE) testing, a functional method for assessing multiple parameters of homeostasis in a single laboratory test performed on whole blood, may be a reasonable next step to achieve improvement in PBM.
The principle of VE testing has been in existence for nearly 70 years – a nidus for clot formation is introduced to whole blood, an activator is added to initiate clotting, and a rotational force is applied, while measuring the size and strength of clot formation over time. This results in a tracing (Figure 1), with associated values that provide detailed information about the functionality of a patient’s ability to achieve hemostasis. A single test can provide information
about the functionality of the coagulation cascade, fibrinogen/fibrin generation, platelets, and eventual clot resolution (Figure 2).
The two platforms that are most commonly used today are thromboelastography (TEG) and rotational thromboelastomertry (ROTEM). Both platforms exhibit very good clinical performance and are based on similar (but distinct) methodologies. The most significant distinction between TEG and ROTEM is the use of different activators of coagulation, which can lead to somewhat different results and transfusion recommendations for a given specimen. Neither platform is “right” or “wrong,” but both must be interpreted in the appropriate clinical context. There is a lot of literature available about these two instruments, and the decision to favor one or the other is very institution-specific. Both TEG and ROTEM can augment standard laboratory coagulation tests, providing additional functional information that is often lacking, which can be essential when deciding what, if any, blood component therapy is most appropriate.
Whether your institution already utilizes VE testing, or is considering introducing it for particular clinical services or in support of a PBM program, it is important to understand what these platforms are capable of and what they are not. Implementing TEG or ROTEM testing is a significant undertaking – consideration must be given to the capital investment, technical performance of the tests, reagent and QC costs, support and maintenance, education of potential users, logistics of test performance (central laboratory versus POC), and interpretation of results. Once these issues have been appropriately addressed, however, TEG and ROTEM can play an important role in the PBM process.
What VE testing adds to the current armament of coagulation testing is a functional assay that, through the use of specific activators and inhibitors, provides data about the functionality of the intrinsic and extrinsic coagulation cascades, fibrinogen/fibrin and fibrinolysis, and platelet contributions to hemostasis. By using different activators and inhibitors, the function of each of these components can be analyzed more specifically.
While such coagulation testing technology has the potential to significantly advance our ability to accurately predict the risk of bleeding and thrombosis, detect the presence of medications affecting coagulation, provide more appropriate blood component therapy, and improve patient outcomes, these claims must be rigorously validated through clinical experience and controlled trials. Determining whether abnormalities detected by these platforms correlate with the actual clinical risk of bleeding and clotting is a challenging process that requires a significant amount of data.
Here is what the current literature informs about TEG and ROTEM:
Predictors of coagulopathy and bleeding
The ability to identify patients at risk for severe hemorrhage would greatly aid in its management. Specifically, trauma-induced coagulopathy (TIC) is being recognized as a clinical entity that contributes to increased bleeding complications. Studies utilizing VE testing have variously concluded that this testing may predict TIC and bleeding risk (1), though a recent Cochrane review (2) showed relatively poor diagnostic accuracy in predicting TIC compared to traditional coagulation tests. It is clear that more research is needed to confirm either of these findings.
Re-exploration in cardiac surgery is another metric that is used to assess the ability of VE-based protocols to decrease bleeding. A recent meta-analysis of VE testing in cardiac surgery suggests a highly significant reduction in re-exploration by incorporating VE testing (3), and an early Cochrane review (4) identified that VE-guided transfusion strategies reduced clinical bleeding. More studies will be needed to definitively conclude the ability of these platforms to identify bleeding risk and reduce clinical bleeding. Importantly, more research also may be necessary to validate the diagnostic accuracy of VE testing.
Reducing blood product transfusion
Multiple studies and meta-analyses have concluded that a VE-guided transfusion strategy reduces overall product usage, specifically resulting in decreased transfusion of RBCs, plasma and platelets (3-6). Compared to traditional coagulation tests, VE-based transfusion results in more restrictive practices, and is more cost-effective (6). While this may lead some to argue that VE testing can realistically replace traditional coagulation tests (6), I believe such a drastic change in practice may not be effective. There is value in interpreting both testing methodologies in clinical context, and it would be imprudent to replace testing methodologies with which many physicians are very familiar, with new methodologies they may not yet fully understand. While this may become a reality sometime in the future, I believe there is still value in maintaining traditional testing. This is especially evident when we consider that VE testing may not yet be fully clinically validated for diagnostic accuracy (2).
It is challenging for any laboratory testing methodology to result in significant improvements in morbidity/mortality, but it is the goal of incorporating VE-based protocols to achieve such advances. Most studies looking at clinical outcomes and mortality, however, do not identify significant improvements by utilizing VE testing compared to traditional coagulation tests (1, 4). The recent meta-analysis of VE testing in cardiac surgery (3), however does find that VE-guided transfusion practices resulted in lower post-operative acute kidney injury (AKI) and thromboembolic events, though there was no association with decreased overall mortality. While these findings are promising, more studies will be needed to definitively identify clinical outcomes that can be improved by incorporating VE testing.
Overall, there appears to be significant promise for these platforms to improve patient care, specifically through improvements in PBM. Incorporating new testing platforms may be challenging, but can result in significant savings and advances in the delivery of patient care.
(1) Crit Care. 2014 Sep 27;18(5):518. doi: 10.1186/s13054-014-0518-9.
(2) Cochrane Database Syst Rev. 2015 Feb 16;(2):CD010438. doi: 10.1002/14651858.CD010438.pub2.
(3) J Surg Res. 2016 Jun 15;203(2):424-33. doi: 10.1016/j.jss.2016.03.008.
(4) Cochrane Database Syst Rev. 2011 Mar 16;(3):CD007871. doi: 10.1002/14651858.CD007871.pub2.
(5) Transfus Med Rev. 2013 Oct;27(4):213-20. doi: 10.1016/j.tmrv.2013.08.004.
(6) Health Technol Assess. 2015 Jul;19(58):1-228, v-vi. doi: 10.3310/hta19580.
Author: Alex Ryder, M.D., Ph.D.
 TEG Platelet Mapping is available in the US to detect ADP and AA platelet inhibition. ROTEM Platelet is available in Europe, and the availability of a platelet receptor assay in the US is likely over a year away. Both TEG and ROTEM are developing assays to detect novel oral anticoagulants. ECATEM is available for this purpose in Europe, but not yet in the US.