Background: Viscoelastic haemostatic assays (VHA) now supersede laboratory assessments for the perioperative assessment and management of coagulation. Despite being used interchangeably in clinical practice, the devices in current use have rarely been directly compared.

Aims: This study directly compared standard laboratory coagulation tests and the two most commonly used VHA devices—TEG6s and ROTEMSigma—in a setting where large fluctuations in coagulation status are typical, to determine associations and interchangeability between key coagulation measures.

Methods: Patients undergoing cardiac surgery (requiring cardiopulmonary bypass) or interventional (transcatheter aortic valve implantation or percutaneous coronary intervention) were recruited prospectively. Blood samples (n=164) were obtained at four timepoints (see Figure1). Each sample was assessed concurrently for standard laboratory tests (PT/INR, aPTT, thrombin clotting time, platelet count, direct fibrinogen), complete+hep(ROTEMSigma), and citrated(TEG6s) cartridges.

Time points for sample collection: T1, baseline; T2, post-heparin administration; T3, post-protamine reversal; and, T4, six-hours postoperatively.

Results: TEG6s required significantly less blood per test than ROTEMSigma (300uL vs. 1.8mL). Conversely, TEG6s is an open system requiring pipetting, whereas ROTEM is entirely enclosed. For intrinsically-activated assays, strong correlations existed for both ‘time to initiation of clot formation’ (CT-INTEM vs. R-CK=0.81; CT-INTEM vs. R-CRT=0.89) and clot strength (MCF-INTEM vs. MA-CK, r=0.81; MCF-INTEM vs. MA-CRT, r=0.87). For extrinsically-activated assays, a strong correlation existed for clot strength (MCF-EXTEM vs. MA-CRT, r=0.89), but not ‘time to initiation of clot formation’ (CT-EXTEM vs. R-CRT, r=0.34). Particularly important for both cardiac surgery and trauma settings is that measurements of the fibrinogen contribution to clot strength were highly correlated (MA-CFF vs. MCF-FIBTEM, r=0.94) and correlated with standard laboratory fibrinogen levels (fibrinogen vs. MA-CFF, r=0.85; fibrinogen vs. MCF-FIBTEM, r=0.86). Poor correlation was evident assessing time to clot formation between the two systems’ heparinase channels (CT-HEPTEM vs. R-CKH, r=0.53) and clot strength (MCF-HEPTEM vs. MA-CKH, r=0.53).

Conclusions: Though ROTEMSigma and TEG6s are strongly correlated in some measurements, they are poorly correlated in others, suggesting that their results, and therefore clinical use, are not interchangeable.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/viscoelastic-haemostatic-assay-comparison-for-perioperative-coagulation-assessment/