PO57 | Direct oral anticoagulant determination in urine samples compared to plasma concentrations in outpatients with atrial fibrillation and obesity

Background: With atrial fibrillation (AF) and high thromboembolic risk need anticoagulant therapy. Few data are available on direct anticoagulants (DOACs) in this population and a point-of-care method has been validated to support rapid clinical decisions and to identify on-off threshold plasma concentrations. The aim of the present study was to evaluate the sensitivity, specificity, positive and negative predictive values (PPV and NPV) of testing for DOACs from urine samples of obese patients taking DOACs for AF. Methods: Cross-sectional study on obese AF outpatients referring to Policlinico Umberto I of Rome. Inclusion criteria were patients of both sexes, aged ≥18 years, Body Mass Index (BMI) ≥30 Kg/m² and receiving a DOAC for AF over at least 7 days. Exclusion criteria were denial of written informed consent, inability to provide a spontaneous urine sample, any contraindication to the administration of DOACs and conditions with known haematuria and blood components such as urobilinogen, which alter the colour of urine and may compromise the interpretation of pad colours of DOAC dipstick. patients were consecutevly enrolled from 2022 to 2024. Trough and peak plasma concentrations and urinary Dipstick were assessed, which determines separate pads for factor Xa (FXA-i) and thrombin inhibitor (THR-i) DOACs. Study endpoints were the sensitivity, specificity, positive and negative predictive values (PPV and NPV) of DOAC Dipstick compared to plasma concentrations. Sub-analysis according to obesity severity and type of DOAC was performed. The study was approved by the local ethic committee of Sapienza University (No. 0234/2022) and was conducted according to the 1975 Declaration of Helsinki. Results: 320 paired plasma and urine samples were available from 160 enrolled patients (mean age 73.2±9.1 years). Comparing to trough plasma concentrations, DOAC Dipstick showed a sensitivity (mean, 95% confidence interval, CI) of 99.24% (95.82-99.98), specificity of 6.89% (0.85-22.76), PPV 82.80% (81.32-84.18), NPV 66.67% (15.79-95.52). On the other hand, comparing to peak plasma concentrations, DOAC Dipstick showed a sensitivity of 97.8% (93.7-99.5), specificity of 0% (0.0-15.4), PPV of 85.9% (85.6-86.2). Urinary Dipstick showed a sensitivity of 99.10% (95.4-100.0), specificity of 4.70% (0.60-16.20) and a PPV and NPV of 74.50% (73.2-75.8) and 66.70 (15.7-95.6), compared to plasma thresholds >30 ng/mL of FXA-I and THR-I. Sub analyses showed similar results between FXA-I and THR-i. Conclusions: The urine point-of-care has high sensitivity, acceptable PPV, but low specificity and NPV in AF obese patients.