Key result
A nomogram using LMWH anti-Xa values accurately predicted DOAC concentrations, with LMWH anti-Xa <0.64 IU/mL and <0.71 IU/mL predicting apixaban and rivaroxaban <50 ng/mL with true positive rates of 94.7% and 100%, respectively.
Why the study?
Specific DOAC assays to guide reperfusion therapy in acute ischemic stroke are not widely available compared to LMWH anti-Xa activity.
Does a nomogram based on LMWH anti-Xa assay accurately predict apixaban and rivaroxaban concentrations compared to specific DOAC assays?
Observational (n=601)
No
Does a nomogram based on LMWH anti-Xa assay accurately predict apixaban and rivaroxaban concentrations compared to specific DOAC assays?
A novel nomogram accurately predicts apixaban and rivaroxaban concentrations using widely available LMWH anti-Xa assays, potentially expanding eligibility for thrombolysis in acute ischemic stroke patients on DOACs.
Anti-Xa thresholds may inform thrombolysis eligibility in DOAC-treated AIS; leaves open whether specific assays outperform heparin-calibrated measures.
BACKGROUND AND PURPOSE: In patients with acute ischemic stroke (AIS) using a direct oral factor-Xa anticoagulant (DOAC) during the last 48 hours, a fixed plasma heparin-calibrated anti-Xa activity (0.5 IU/mL) was proposed as a threshold below which patients could be eligible for thrombolysis and/or thrombectomy. Besides, specific DOAC-calibrated anti-Xa thresholds up to 50 ng/mL have been proposed. However, specific DOAC assays are not widely available contrarily to low-molecularweight heparin (LMWH) anti-Xa activity. We developed and validated a nomogram for predicting apixaban and rivaroxaban concentrations based on LMWH anti-Xa assay. METHODS: Our prospective study included apixaban (n=325) and rivaroxaban (n=276) patients. On the same sample, we systematically measured specific DOAC concentration and LMWH anti-Xa activity, using STA®-Liquid-Anti-Xa (Stago) and specific DOAC- or LMWH-calibrators, respectively. The nomogram was built using quantifiable values for both assays on the derivation cohorts with a log-linear regression model. Model performances including sensitivity, specificity, and true positive rate for different thresholds were checked on the validation cohorts. RESULTS: The models built from the derivation cohorts predicted that values <30 ng/mL and <50 ng/ mL DOAC thresholds corresponded to LMWH-anti-Xa values <0.10 IU/mL and <0.64 IU/mL for apixaban; <0.10 IU/mL and <0.71 IU/mL for rivaroxaban. The model accurately predicted apixaban/ rivaroxaban concentrations in the validation cohort. CONCLUSIONS: This easy-to-use nomogram, developed with our reagent, allowed accurately predicting DOAC concentrations based on LMWH-anti-Xa results in emergency situations such as AIS when drug-specific assessments are not rapidly available. Using DOAC <50 ng/mL equivalent threshold, instead of the fixed LMWH <0.5 IU/mL one, would allow proposing thrombolysis to more patients.
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Brakta et al. (2023) conducted an observational in Patients on apixaban or rivaroxaban referred for hemostasis testing prior to thrombolysis or thrombophilia screening (n=601). LMWH anti-Xa assay vs. Specific DOAC concentration assay was evaluated on True positive rate for predicting apixaban concentration <50 ng/mL using LMWH anti-Xa <0.64 IU/mL (95% CI 74.0-99.9). A nomogram using LMWH anti-Xa values accurately predicted DOAC concentrations, with LMWH anti-Xa <0.64 IU/mL and <0.71 IU/mL predicting apixaban and rivaroxaban <50 ng/mL with true positive rates of 94.7% and 100%, respectively.
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