Acute ischemic stroke and measurement of apixaban and rivaroxaban: an observational cohort implementation study

Treatment with intravenous thrombolysis for acute ischemic stroke is contraindicated with intake of apixaban/rivaroxaban in the last 48 hours. Recent European Stroke Organization guidelines suggest that thrombolysis can be considered if anti-factor Xa activity (AFXa) is <0.5 × 10³ IU/L with low-molecular-weight (LMWH) or unfractionated heparin (UFH) calibrated assays. Some centers also use apixaban/rivaroxaban-calibrated AFXa assays to identify patients with low drug concentrations.

To prospectively evaluate the first year of implementation of drug-calibrated AFXa assays at our center with 2500 yearly admittances with suspected stroke.

Samples were analyzed on Sysmex CS-5100 instruments with Innovance anti-Xa reagents. Thrombolysis could be considered with drug concentrations <25 μg/L. Patients were registered in an institutionally approved quality register. Outcomes included (1) the number of patients receiving thrombolysis after drug measurement, (2) turn-around time for drug concentration measurements, and (3) sensitivity of LMWH/UFH AFXa to apixaban and rivaroxaban.

Apixaban or rivaroxaban was measured in 148 samples, and 4 patients who previously would have been ineligible for thrombolysis were treated with thrombolysis. In total, thrombolysis was administered in 123 patient episodes in the study period. The median turn-around time for the drug measurements was 38 minutes. Apixaban concentrations of 25 μg/L and 50 μg/L corresponded to LMWH/UFH AFXa of 0.13 and 0.27 × 10³ IU/L, respectively. There were too few rivaroxaban results for regression analysis.

Implementation of apixaban and rivaroxaban measurements led to a small increase in the number of patients receiving thrombolysis. Excluding significant concentrations of apixaban or rivaroxaban using LMWH/UFH AFXa may be feasible.