Program: Oral and Poster Abstracts
Session: 332. Antithrombotic Therapy: Poster I
Objectives: To assess if stability of warfarin anticoagulation monitored by PT and Fiix-PT was affected differently by gender.
Methods: This study is a subgroup analysis of the prospective, randomized, double-blind Fiix-trial. A subgroup of 815 atrial fibrillation patients on long-term warfarin monitored with Fiix-PT (Fiix-warfarin patients) or PT (PT-warfarin patients) were assessed in an intention-to-monitor manner by comparing surrogate anticoagulation indicators such as dose and dose frequency, time in therapeutic range (TTR, Rosendaal method) and variance growth rate of the INR (VGR; an indicator of INR fluctuation size).
Results: Baseline parameters between the 396 Fiix-warfarin and 419 PT-warfarin patients did not differ. The median observation time was 1.4 years. Fiix-warfarin patients had more tests within therapeutic range (66% vs 63%, p=0.0019) and fewer tests below range (19% vs 21%, p=0.0061) than PT-warfarin patients. The test-in-range improvement observed with Fiix-warfarin over that with PT-warfarin was mainly explained by an improvement observed in women, i.e. the fraction of monitoring tests within range was higher (64% vs 59%, p=0.0001) and the fraction below range was lower (20% vs 24%, p=0.0002) in women on Fiix-warfarin. Likewise, with Fiix-warfarin TTR was higher (81% compared with 79%) and this was mainly explained by higher TTR in women on Fiix-warfarin (80%) than in women on PT-warfarin (75%; p=0.0401). Little difference was observed in TTR in men. The INR varied less with Fiix-warfarin than with PT-warfarin (VGRB1 0.20 vs 0.24, p=0.0810). There was significantly more variation in VGR in women than in men. Thus, Fiix-warfarin men vs women had a VGRB1 of 0.18 vs 0.25, p=0.0372, and PT-warfarin men vs women had VGRB1 0.21 vs 0.30, p=0.0056. A trend for fewer annual dose changes with Fiix-warfarin than with PT-warfarin was observed (5.6 vs 6.2 annually, p=0.0822) and this was mainly explained by 20% fewer annual dose changes with Fiix-warfarin than with PT-warfarin in women (6.0 vs 7.4, p=0.0342). Also, there were fewer dose changes per monitoring test in Fiix warfarin women (0.27 vs 0.32, p=0.0292). Finally, women treated with Fiix-warfarin used a lower median daily warfarin dose than women treated with PT-warfarin (3.4 vs 4.2 mg, p=0.0029).
Conclusions: Monitoring warfarin with the Fiix-PT improved the stability of warfarin anticoagulation and reduced the daily dose significantly in women. A non-significant but consistent smaller effect in the same direction was seen in men.
Disclosures: Gudmundsdottir: Fiix Diagnostics Ltd.: Equity Ownership , Patents & Royalties: Patent pending for Fiix prothrombin time . Onundarson: Fiix Diagnostics Ltd: Equity Ownership , Patents & Royalties: Patent pending status for Fiix prothrombin time .
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