Preliminary insights into monitoring bivalirudin anticoagulation: A retrospective cohort study of aPTT versus a chromogenic anti-IIa assay

Background: Bivalirudin infusions are traditionally monitored with activated partial thromboplastin time (aPTT) despite the poor correlation with bivalirudin dose-response curves. This discordance may lead to over or under-anticoagulation, predisposing patients to bleeding or thrombosis and repeated dose adjustments. While a chromogenic bivalirudin-specific anti-IIa assay, which measures bivalirudin plasma concentrations, is available, the extent to which this test may improve clinical monitoring and patient outcomes remains unclear. Accordingly, we aimed to retrospectively assess the correlation between the bivalirudin dose and the anti-IIa assay and to establish a therapeutic range. We then performed a retrospective comparative cohort study assessing the impact of anti-IIa monitoring compared to aPTT on patient outcomes. Methods: Plasma samples from adults receiving bivalirudin anticoagulation were analyzed to assess the correlation between bivalirudin dose, aPTT, and the anti-IIa assay. A retrospective comparative analysis was then conducted to evaluate operational and clinical outcomes in patients monitored with aPTT versus the anti-IIa assay. Results: Analysis of 127 samples from 11 bivalirudin-anticoagulated adults showed a very weak correlation between bivalirudin dose and aPTT (r² = 0.08), while a strong correlation was seen with the anti-IIa assay (r² = 0.65). The dose-response slope's coefficient of variation (CV) for the aPTT and anti-IIa assay were 31 % and 6.6 %, respectively. Patients monitored with the anti-IIa assay had significantly higher time in therapeutic range than those monitored with aPTT (92.1 % vs. 26 %, p < 0.001). Conclusions: These findings suggest that the anti-IIa assay provides more reliable bivalirudin monitoring than aPTT, with a significant reduction in minor bleeding.