Interpreting changes in quality of life in atrial fibrillation: How much change is meaningful?

The Atrial Fibrillation Effect on QualiTy of Life (AFEQT) questionnaire is a novel quality of life (QOL) measure previously shown to be valid, reliable, and sensitive to clinical change in patients with atrial fibrillation (AF). The clinical relevance of a given change in the score is not known. The most useful "anchor" for a measure of meaningful change in QOL is patient-reported magnitude of change. The aim of this study was to define the interpretability of changes in the AFEQT score from the patients' perspective. With the use of the original validation study of AFEQT, in which 210 patients completed the questionnaire at baseline and at 3 months, we estimated the AFEQT score corresponding to a meaningful improvement in QOL using the patients' assessments of global change in QOL, AF symptoms from the Atrial Fibrillation Severity Scale (AFSS), and physicians' assessment of global QOL over the 3 months, as anchors. In patients with a moderate improvement in global QOL, the AFEQT scores increased from 51.9 ± 21.8 to 70.8 ± 17.4 (an increase of 18.9 ± 20.7), compared with an increase of 6.9 ± 16.9 units in patients with "unimportant change" in global QOL. Physicians' global assessment yielded a similar change in AFEQT score corresponding to a moderate change in global QOL (21.3 ± 20.2 units). Patients with moderate improvement in AF symptom severity using the AFSS scale had an increase of 17.9 ± 11.8 units on the AFEQT scale. A change in 19 units in the AFEQT score corresponded to a 0.9 SD unit change or greater than a minimal important difference from a distribution based method. A meaningful improvement in QOL in patients with AF can be measured from a change in the AFEQT score. These results can assist in monitoring patient progress and interpreting the effects of interventions in patients with AF.