To the Editor:
In their review “Diagnostic performance and therapeutic consequence of thromboelastometry activated by kaolin versus a panel of specific reagents,” Sorensen et al. 1demonstrate a lack of scientific rigor in the conduct of the investigation, as well as factual omissions.
The authors draw their conclusions regarding thromboelastography (TEG®; Hemoscope, Niles, IL) by choosing a single reagent, kaolin, from the suite of TEG tests; using this reagent in a thromboelastometry analyzer (ROTEM®; Tem International GmbH, Munich, Germany); and then comparing the kaolin results to the full array of ROTEM tests. The mechanics of the two analyzers are quite different, and reagents are precisely designed for their respective systems. In the TEG analyzer, the cup in which the blood is placed oscillates; in the ROTEM analyzer, the pin oscillates while the cup remains fixed. The sample volumes are also different (360 μl for TEG and 340 μl for ROTEM). Although the authors acknowledge these mechanistic differences, they do not believe they impact the results. Unless this is demonstrated by actual data using a TEG analyzer, the scientific validity of the results is compromised.
The authors claim that ROTEM can differentiate between dilutional coagulopathy and thrombocytopenia by applying the FIBTEM functional fibrinogen assay, whereas the kaolin TEG cannot. For this to be a valid observation, the TEG functional fibrinogen assay must be used.
In the discussion of heparin detection, the authors state that heparin-induced coagulopathy can be determined with the ROTEM hep-tem® assay. They neglect to mention that the TEG heparinase cups identify heparin effect for both unfractionated heparin products, and those with low molecular weight. This is a major oversight.
Regarding time to results, the authors state that TEM assay results become available more rapidly than kaolin TEG results. They omit discussion of the RapidTEG assay, which uses both kaolin and tissue factor as activators and which provides an ACT value in seconds and overall clot strength results in 15 min, even in the most coagulopathic patients.2This assay has been used by investigators who have shown that the RapidTEG parameters are predictive of early and massive transfusion in trauma.2,3The authors discuss the predictive value of ROTEM in massive transfusion but omit the TEG studies.
Finally, this paper evaluated healthy volunteers whose blood has been used to simulate clinical situations through the addition of various agents to the cups. A discussion of the use of the two analyzers to predict actual patient outcomes should be based on actual patient data. The lack of scientific validity based on not using a TEG analyzer, combined with the omission of key information regarding universally available TEG reagents and the lack of clinical significance to actual outcomes, contributes to a very misleading profile of TEG. We hope that the authors will clarify their omissions regarding TEG reagents in particular and look forward to the revised notation.