We conducted a prospective observational study determining the interchangeability of the TEG6S and TEG5000 platforms in a cohort of critically ill patients in the intensive care unit of a tertiary hospital. To date, this is the most comprehensive validation study of the TEG6S vs. TEG5000 systems in a critically ill population. We found that the TEG6S and TEG5000 systems were broadly interchangeable. The majority of TEG variables demonstrated almost perfect or substantial agreement, with minimal fixed bias or proportional bias. Exceptions were MA, which demonstrated a fixed, non-proportional bias and LY30%, which demonstrated proportional bias between TEG6S and TEG5000 analysers. Although minor differences in some variables were detected, all variables measured by TEG6S fell within acceptable normal limits. As such, observed differences between TEG6S and TEG5000 were likely clinically insignificant and even the apparent bias in MA (difference 5.2 mm) and difference in LY30% (0.61%) would not likely impact clinical decision-making if within normal limits. This has important implications for use interchangeability of TEG platforms in clinical practice and also for comparing multi-site research programs.
Relationship to previous literature
One published study has reported the agreement between TEG6S and TEG5000 by assessing a cohort of 300 cardiac surgery patients and 157 healthy controls . Results from the TEG6S were compared to standard reference ranges of the TEG5000 system . Similar to our findings, this study demonstrated a strong correlation between the two systems for the standard haemostasis tests (R r = 0.932, MA r = 0.972, LY30% r = 0.938). However, we used Lin’s CC to assess the degree of agreement between each of the coagulation the variables studied, rather than regression analysis, which assesses correlation . Additionally, the study by Gurbel et al. only compared the agreement of TEG5000 and TEG6S in a normocoagulative cohort (i.e. healthy volunteers and simple cardiac revascularisation). Conversely, we examined the agreement of TEG5000 and TEG6S systems in critically ill patients, including those with sepsis and in chronic liver failure, prone to grossly abnormal and less predictable patterns of coagulation [18,19,20,21,22]. Arguably, in a critically ill population where haemostatic failure and derangements of the coagulation system are common, our findings extend the documented clinical interchangeability of the TEG6S and TEG5000 platforms .
Implications of study findings
Our study findings indicate that the TEG5000 and TEG6S devices are broadly interchangeable in the setting of coagulation monitoring in acutely ill patients. This interchangeability was observed across all major components of the coagulation process. In particular, MA seems to generate the strongest concordance between machines. This has particular clinical relevance as the role thrombus strength, and by extension, maximum amplitude, has in determining the global coagulation state is being recognised as increasingly significant [23, 24]. We also found that despite strong concordance between the MA as measured by the TEG5000 and TEG6S devices, a fixed bias was clearly observed. This finding revealed the TEG6S consistently measures MA higher than that of the TEG5000. To our knowledge, our study is the first to demonstrate this. Whether this finding is clinically significant is impossible to infer from this data alone, however as under-estimation or over-estimation of maximum amplitude may have significant decision-making implications (influencing transfusion requirements), it is an important bias to recognise. Whether the TEG5000, or TEG6S more accurately reflects the true coagulation strength also remains unclear. Whether the TEG5000 or the TEG6S is more closely representative of the true coagulation state requires further research, involving comparison to conventional coagulation tests and clinical outcomes, which goes beyond the scope of this study. Of note, one exception to the close concordance between the two devices occurred when examining LY30%, the parameter measuring fibrinolysis. It is unknown why the concordance between the TEG5000 and TEG6S machines was poor in this parameter and further research is necessitated before LY30% can be used as reliable assessment of fibrinolysis in a clinical setting.
Strengths and limitations
Our study has several methodological strengths. This is the first study to use rigorous statistical methodology to determine agreement and interchangeability of the TEG6S and TEG5000 platforms. A single skilled operator, blinded to the results, minimised interoperator confounding. All blood samples were taken using the same sampling methodology, in same facility, and in same time-period. Our study was not without limitations. Firstly, our study examines coagulation assessment in a deliberately heterogeneous cohort of intensive care patients, and studies are needed to determine if our findings are applicable to other complex cohorts of patients e.g. cardiac surgery, liver transplantation. However the results of our study reflect agreement and interchangeability of both TEG systems in clinical context of critically ill patients with profound derangements of coagulation tests. This renders this study generalisable to similar centers with similar clinical workloads. Another limitation was the exclusive examination of the citrated kaolin assay, via arterial sampling. Because of this, we are unable to comment as to whether our data is generalisable to venous samples, and are unable to examine agreement across other assay types. However, as this is the most common assay used, and citrate is the most practical storage medium, analysis of the CK assay allowed for the investigation of clinically relevant comparison across both devices. We included a comparatively small sample size, however it was both adequately powered to allow us to complete our study objectives, and is the largest study of its kind in an acutely ill population. Finally, our study was non-interventional, observational research, and subsequently did not have the power to allow authors to compare the diagnostic utility of TEG6S and TEG5000 for clinical outcomes, however, this was not the intention of this study. Conversely, we deliberately aimed to conduct a purely observational study in order to compare and validate a new and existing technology in a controlled, non-interventional setting, in order to provide a complete and minimally biased assessment of an increasingly popular global coagulation assessment tool.