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Comparison of international normalized ratio audit parameters in patients enrolled in GARFIELD‐AF and treated with vitamin K antagonists
Author(s) -
Fitzmaurice David A.,
Accetta Gabriele,
Haas Sylvia,
Kayani Gloria,
Lucas Luciardi Hector,
Misselwitz Frank,
Pieper Karen,
Cate Hugo,
Turpie Alexander G. G.,
Kakkar Ajay K.
Publication year - 2016
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/bjh.14084
Subject(s) - medicine , atrial fibrillation , confidence interval , vitamin k antagonist , warfarin , concordance , cardiology , gastroenterology
Summary Vitamin K antagonist ( VKA ) therapy for stroke prevention in atrial fibrillation ( AF ) requires monitoring of the international normalized ratio ( INR ). We evaluated the agreement between two INR audit parameters, frequency in range ( FIR ) and proportion of time in the therapeutic range ( TTR ), using data from a global population of patients with newly diagnosed non‐valvular AF , the Global Anticoagulant Registry in the FIELD –Atrial Fibrillation ( GARFIELD ‐ AF ). Among 17 168 patients with 1‐year follow‐up data available at the time of the analysis, 8445 received VKA therapy (±antiplatelet therapy) at enrolment, and of these patients, 5066 with ≥3 INR readings and for whom both FIR and TTR could be calculated were included in the analysis. In total, 70 905 INR s were analysed. At the patient level, TTR showed higher values than FIR (mean, 56·0% vs 49·8%; median, 59·7% vs 50·0%). Although patient‐level FIR and TTR values were highly correlated (Pearson correlation coefficient [95% confidence interval; CI ], 0·860 [0·852–0·867]), estimates from individuals showed widespread disagreement and variability (Lin's concordance coefficient [95% CI ], 0·829 [0·821–0·837]). The difference between FIR and TTR explained 17·4% of the total variability of measurements. These results suggest that FIR and TTR are not equivalent and cannot be used interchangeably.