Defining clinically important difference in the atrial fibrillation effect on quality-of-life score: Results from the outcomes registry for better informed treatment of atrial fibrillation

Background: The Atrial Fibrillation Effect on Quality-of-Life (AFEQT) questionnaire has recently been validated to measure the impact of atrial fibrillation on quality of life, but a clinically important difference in AFEQT score has not been well defined. Methods and Results: To determine the clinically important difference in overall AFEQT (score range= 0 [worst] to 100 [best]) and selected subscales, we analyzed data in the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) registry, a United States-based outpatient atrial fibrillation registry. AFEQT was assessed at baseline and 1 year in a subset of 1347 ORBIT-AF patients from 80 US sites participating in ORBIT-AF from June 2010 to August 2011. The mean change method was used to relate changes in 1-year AFEQT scores to clinically important changes in the physician assessment of European Heart Rhythm Association functional status (1 class improvement and separately 1 class deterioration). Clinically important differences and 95% CI corresponding to either a 1 European Heart Rhythm Association class improvement or deterioration were 5.4 (3.6-7.2) and-4.2 (-6.9 to-1.5) AFEQT points, respectively. Similarly, clinically important difference values were seen for a 1 European Heart Rhythm Association class improvement for the AFEQT subscales Activities of Daily Living and Symptoms: 5.1 (2.5-7.6) and 7.1 (5.3-9.0) AFEQT points, respectively. Conclusions: Based on the anchor of 1 European Heart Rhythm Association class change, changes in AFEQT score of + or-5 points are clinically important changes in patients' health. Clinical Trial Registration: URL: https://clinicaltrials.gov. Unique identifier: NCT01165710.