Thromboelastography (TEG) and Rotational Thromboelastometry (ROTEM) are viscoelastic blood tests that provide a dynamic, whole-blood assessment of clot formation and stability. Unlike traditional coagulation assays such as prothrombin time (PT) or activated partial thromboplastin time (aPTT), which only assess individual components of the coagulation cascade, these viscoelastic tests evaluate the full process—from the initiation of clotting to clot firmness and eventual fibrinolysis (1). This global approach allows clinicians to see how plasma proteins, platelets, and fibrin interact in real time, which is particularly useful in high-risk settings like trauma, cardiac surgery, and liver transplantation. Although both systems operate on similar principles, they differ in the specifics of their approaches.
In TEG, a small sample of whole blood is placed in a cup that gently oscillates back and forth. A pin is suspended in the blood, and as the clot begins to form, its growing stiffness transmits torque to the pin through fibrin strands. This mechanical movement is converted into an electrical signal that produces a graphical trace, or thromboelastogram, illustrating various phases of clot formation. ROTEM operates based on the same physical concept, but with an inverted setup: the cup remains stationary while the pin rotates. This design, along with optical detection instead of mechanical torque, minimizes vibration artifacts and makes ROTEM more reproducible in clinical environments (1).
Although thromboelastography and rotational thromboelastometry produce similar output curves, they are not interchangeable. The main difference between the two lies in their assay reagents and activation pathways. ROTEM employs reagents such as INTEM (for intrinsic pathway activation), EXTEM (for extrinsic pathway activation), and FIBTEM, which includes a platelet inhibitor to assess fibrinogen function. TEG, meanwhile, uses kaolin or tissue factor as activators and can include a Platelet Mapping assay to measure platelet reactivity to antiplatelet medications such as aspirin or clopidogrel (2). While both instruments assess clot strength and kinetics, this distinction means that ROTEM provides easier standardization across centers, whereas TEG offers more flexibility for platelet and drug response studies.
These technologies have significantly improved transfusion management in cardiac surgery and trauma care. While conventional laboratory tests can take up to an hour, TEG and ROTEM provide results in under ten minutes, which is critical for patients experiencing rapid blood loss. In a prospective clinical trial, Weber et al. (2012) demonstrated that using viscoelastic testing to guide transfusion decisions resulted in significantly fewer blood transfusions and lower costs compared to standard laboratory-based strategies (3). These findings, along with those of other studies, have influenced European and American guidelines, which now recommend point-of-care viscoelastic testing as the primary method for managing perioperative bleeding.
Thromboelastrography and rotational thromboelastometry are also valuable for monitoring anticoagulant and antiplatelet therapy. ROTEM clotting time has been shown to correlate with plasma levels of direct thrombin inhibitors, such as dabigatran. TEG, on the other hand, shows sensitivity to these drugs, as well as to overall platelet function (1). However, both systems have limitations. Results can vary based on temperature, calcium concentration, or pH. Additionally, there is no universal standardization of reagents or reference ranges between centers. Despite these limitations, viscoelastic testing provides clinicians with a more complete, patient-specific view of hemostasis, helping them tailor therapy to individuals rather than relying on population-based norms.
In summary, thromboelastography and rotational thromboelastometry are major advancements in coagulation testing. These techniques provide real-time insights into clot formation, strength, and breakdown, extending beyond static laboratory measurements. Although their underlying principles are similar, their operational differences make each system well-suited to different clinical and research environments. Together, TEG and ROTEM are shifting modern coagulation management toward personalized, data-driven care, improving patient safety and outcomes.
References
1. Korpallová B, Samoš M, Bolek T, et al. Role of Thromboelastography and Rotational Thromboelastometry in the Management of Cardiovascular Diseases. Clin Appl Thromb Hemost. 2018;24(8):1199-1207. doi:10.1177/1076029618790092
2. Bolliger D, Seeberger MD, Tanaka KA. Principles and practice of thromboelastography in clinical coagulation management and transfusion practice. Transfus Med Rev. 2012;26(1):1-13. doi:10.1016/j.tmrv.2011.07.005
3. Weber CF, Görlinger K, Meininger D, et al. Point-of-care testing: a prospective, randomized clinical trial of efficacy in coagulopathic cardiac surgery patients. Anesthesiology. 2012;117(3):531-547. doi:10.1097/ALN.0b013e318264c644