title: Warfarin-related outcomes in patients with antiphospholipid antibody syndrome managed in an anticoagulation clinic.
abstract: Patients with antiphospholipid antibody syndrome (APA) are at elevated risk of venous and arterial thromboembolic complications. Oral anticoagulation with warfarin is recommended for secondary prevention of thromboembolism, but warfarin-related outcomes have not been systematically investigated when warfarin therapy is managed by a dedicated anticoagulation clinic. The objectives of the study were to evaluate warfarin-related monitoring outcomes, clinical endpoints and the use of healthcare resources as a result of warfarin-related complications in patients with APA compared to a group of patients without APA, all of whom were managed in an anticoagulation clinic setting. A retrospective observational cohort design was used to investigate patients with and without APA, all of whom had a history of venous or arterial thromboembolism, and were matched for age, gender and indication for oral anticoagulation. Thirty-six APA patients taking warfarin were compared to a matched cohort of 36 patients without APA. Monitoring outcomes (time in therapeutic range, clinic visits per year, frequency of warfarin dosing adjustments, reasons for out-of-range INRs) were similar between groups, as was the frequency of major bleeding complications (3.2%/pt-yr vs. 3.1%/pt-yr). However, recurrent thromboembolic events (9.6%/pt-yr vs 0) occurred more frequently in APA patients. APA patients required more emergency room visits (6.4%/pt-yr vs. 1.6%/pt-yr) and hospital admissions (14.4%/pt-yr vs.3.0%/pt-yr) to manage complications of warfarin therapy. In conclusion, despite similar monitoring outcomes obtained in a dedicated anticoagulation clinic setting, adverse clinical outcomes are significantly more frequent in patients with APA syndrome than in those without APA, and require more frequent use of healthcare resources.
authors.affiliation: University of Washington, School of Pharmacy, Seattle, WA 98195, USA. akwitt@u.washington.edu
authors.forename: Ann K
authors.initials: AK
authors.lastname: Wittkowsky
authors.forename: Jennifer
authors.initials: J
authors.lastname: Downing
authors.forename: Juan
authors.initials: J
authors.lastname: Blackburn
authors.forename: Edith
authors.initials: E
authors.lastname: Nutescu
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000494:pharmacology*; D016736:Antiphospholipid Syndrome / Q000188:drug therapy* / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013927:Thrombosis; D016896:Treatment Outcome; D014859:Warfarin / Q000494:pharmacology*
chemical_list: D000925:Anticoagulants; D014859:Warfarin