Comparison of international normalized ratio audit parameters in patients enrolled in GARFIELD-AF and treated with vitamin K antagonists

David A. Fitzmaurice, Gabriele Accetta, Sylvia Haas, Gloria Kayani, Hector Lucas Luciardi, Frank Misselwitz, Hugo ten Cate, Alexander G.G. Turpie, Ajay K. Kakkar, GARFIELD-AF Investigators

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Abstract

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 INRs 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.
Original languageEnglish
Pages (from-to)610-623
Number of pages14
JournalBritish Journal of Haematology
Volume174
Issue number4
DOIs
Publication statusPublished - 1 Aug 2016

Cite this

Fitzmaurice, D. A., Accetta, G., Haas, S., Kayani, G., Lucas Luciardi, H., Misselwitz, F., ten Cate, H., Turpie, A. G. G., Kakkar, A. K., & GARFIELD-AF Investigators (2016). Comparison of international normalized ratio audit parameters in patients enrolled in GARFIELD-AF and treated with vitamin K antagonists. British Journal of Haematology, 174(4), 610-623. https://doi.org/10.1111/bjh.14084