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

Background: 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.

Objective: The aim of this study was to define the interpretability of changes in the AFEQT score from the patients' perspective.

Methods: 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.

Results: 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.

Conclusions: 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.