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

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.