Abstract Body: Background
Prior treatment with Factor Xa inhibitors (OAC) within 48 hours is a contraindication to intravenous thrombolysis (IVT) in patients with acute ischemic stroke (AIS). Given the time restrictions of IVT treatment and existing Xa activity assays, these patients are usually disqualified for IVT. In a recent study, 80% of vascular neurologists would consider IVT in OAC patients if a well-designed study demonstrated safety. A binary point-of-care urine test (POCUT; DOASENSE www.doasense.de) is positive with plasma OAC levels above 30 ng/mL considered the threshold for anticoagulant activity, and results within ten minutes of sampling. We report preliminary data of an ongoing study aimed to validate the accuracy of this POCUT and evaluate its impact on AIS treatment decisions.

Methods
We prospectively enrolled patients with history of probable OAC use evaluated for AIS treatment in the emergency department of a comprehensive stroke center. Acquisition of the urine sample and a plasma anti-Xa (aXa) assay were integrated into the standard AIS protocol. Test results were not used to guide treatment decisions, but the stroke team was asked the potential impact of the POCUT test result on their treatment decision assuming the POCUT test was reliable. The POCUT result was later validated against the aXa assay (Diagnostica Stago Rotachrom^R reported in low molecular weight heparin international units [IU]). AXa levels > 0.4 IU/mL correlate with plasma OAC > 30 ng/ml. Informed consent was obtained in all patients.

Results
Baseline characteristics and results for the 11 patients enrolled to date are in Table 1. All patients endorsed treatment with Apixaban median 12hr 15 min earlier (IQR 339-1060 min). The POCUT was positive in 9 patients; 8 of these correlated with a positive aXa level; the aXa level was not obtained in 1 patient. Two negative POCUTs correlated with negative aXa levels. The stroke team did not treat any of the 11 patients with IVT. The POCUT result may have impacted the treatment decision in 7 (64%) patients and would have resulted in IVT treatment in 2 (18%).

Conclusion
Our results suggest that the POCUT can reliably detect therapeutic OAC levels and may be useful for acute stroke treatment decisions. A larger sample size of positive and negative POCUT patients is planned to confirm these findings prior to embarking on a study to determine the safety of using the test for treatment decisions.