Method Comparison Analysis of Quantra Relative to Rotational Thromboelastometry and Conventional Coagulation Testing in Cardiac Surgery

Background: Perioperative utilization of viscoelastic testing to guide the hemostatic management of patients undergoing cardiac surgery is recommended. Historically thromboelastography (TEG) and rotational thromboelastometry (ROTEM) have been used in this setting. The Quantra platform is a new cartridge-based, point-of-care, viscoelastic testing device that utilizes ultrasound to characterize dynamic changes in the viscoelastic properties of blood during clot formation. At present, limited studies addressing the interchangeability of viscoelastic testing parameters exist. Consequently, we conducted a method comparison of Quantra relative to rotational thromboelastometry (ROTEM) and conventional coagulation testing (CCT) in patients undergoing surgery requiring cardiopulmonary bypass (CPB).

Aims: This study aimed to assess the correlation and agreement between Quantra, ROTEM, and CCT results using blood samples from cardiac surgery patients.

Methods: Blood samples were collected during cardiopulmonary bypass from 127 adult patients undergoing cardiac surgery requiring CPB (after rewarming to 36°C) and before protamine administration. Samples were evaluated in parallel using Quantra, ROTEM, and CCT. Quantra parameters using the QPlus Cartridge included clot time (CT), heparinase clot time (CTH), clot time ratio (CTR), clot stiffness (CS), fibrinogen (FCS), and platelet (PCS) contributions to CS. ROTEM measurements assessed included CT, clot firmness at 20 minutes (A20) and maximum clot firmness (MCF). CCTs included PT, PTT, fibrinogen concentration, and platelet count. Method comparison analyses were performed using Deming Regression to assess the correlation between comparable parameters of Quantra, ROTEM, and CCT. To compare CS and A20/MCF parameters, ROTEM clot amplitudes were transformed from millimeter to Pascals using a conversion formula [((500*mm)/(100-mm))/100]. Individual test results were evaluated for agreement of clinical classifications (low, hemostatic function decreased; normal, hemostatic function within established reference range; high, hemostatic function elevated) relative to reference intervals using a clinical composite index (CCI).

Results: Deming regression analysis demonstrated a moderate to very strong correlation between Quantra and ROTEM parameters, with r_s values between 0.56 to 0.91 (Table 1). A strong correlation was observed between FCS and fibrinogen concentration and PCS and platelet count (r_s=0.77 and r_s=0.70, respectively). Despite showing acceptable correlation, Deming regression showed significant constant and proportional biases when comparing comparable parameters. As assessed by the CCI, the overall percent agreement between the Quantra and ROTEM parameters and Quantra and CCT were 64% to 82% (Table 2) and 50% to 72%, respectively. Analysis of agreement between each modality using Cohen's weighted kappa indicated fair to a substantial agreement between Quantra and ROTEM parameters and slight to moderate agreement between Quantra and CCTs parameters.

Conclusion: Findings from this method comparison demonstrate that Quantra parameters correlated strongly with corresponding parameters from ROTEM and CCT. However, observed biases following Deming regression analysis indicate that these viscoelastic platforms are not interchangeable; local reference ranges should be established before adopting and clinical use of alternative platforms.

Sarode:Cerus: Research Funding; Siemens: Research Funding; Takeda: Research Funding; CSL Behring: Consultancy; Octapharma: Consultancy; VarmX: Consultancy.