Urine-based point-of-care detection of direct oral anticoagulant activity in acute stroke : accuracy at anti-Xa thresholds relevant for intravenous thrombolysis

Abstract

Background: Rapid assessment of direct oral anticoagulant (DOAC) activity is essential in acute ischemic stroke (AIS), particularly because intravenous thrombolysis (IVT) may be considered at anti-Xa levels ≤ 100 ng/mL. Laboratory drug-specific assays; however, are often limited by availability and turnaround time. A urine-based point-of-care (POC) test may provide a rapid alternative. Objectives: To determine the diagnostic accuracy of a urine-based POC dipstick for detecting clinically relevant DOAC activity at (1) the established screening threshold (≥30 ng/mL) and (2) the IVT-relevant threshold (≥100 ng/mL), using calibrated plasma DOAC levels as a reference standard. Methods: In this prospective diagnostic accuracy study (UPTURN trial), consecutive AIS patients underwent urine-based POC testing. Dipstick results, recorded as visual and automatic readouts, were analyzed against plasma DOAC activity. Relevant anticoagulant activity was defined as anti-Xa ≥30 ng/mL; the IVT eligibility threshold was defined as anti-Xa <100 ng/mL. Factor Xa inhibitors were quantified using drug-specific chromogenic anti-Xa assays; dabigatran activity was measured using Biophen DTI. Diagnostic accuracy metrics were calculated with exact 95% CIs. Time-to-result was compared between POC testing and plasma assays. Results: Among 101 AIS patients (55 with DOAC intake), the urine-based dipstick test reliably identified relevant anticoagulatory activity (anti-Xa ≥30 ng/mL) with a sensitivity of 100% and specificity of 96.3% (automated readout). Visual interpretation yielded similar accuracy. For higher anti-Xa levels (≥100 ng/mL), sensitivity remained 100%, though specificity decreased (74.4%). A double-positive visual result increased specificity to 92.8% at 84.4% sensitivity. Median time to result was 19 minutes for urine testing versus 144 minutes for blood-based assays. Test performance was consistent across DOAC agents, dosages, and intake timing. Visual grading enabled semiquantitative discrimination of DOAC levels. Conclusion: Urine-based DOAC dipstick testing is a rapid, accurate, and reliable method for detecting anticoagulatory activity in AIS patients, providing a valuable tool to guide acute therapeutic decisions. Future studies are warranted to validate its clinical impact and broader applicability, especially in the emergency setting.