Abstract 130: Clinically Important Difference in the Atrial Fibrillation Effect on QualiTy-of-Life (AFEQT) Score: Results from the ORBIT-AF Registry

Background: The Atrial Fibrillation Effect on QualiTy-of-Life (AFEQT) survey has recently been validated to measure the impact of atrial fibrillation on patients’ quality of life, but a clinically important difference (CID) in AFEQT score has not been defined. Knowing the CID is needed to interpret the meaningfulness of differences between treatments in clinical trials; or patient populations for quality assessment.Objectives: To calculate CID values in AFEQT in the ORBIT registry.Methods: ORBIT-AF is a US-based outpatient AF registry that measured disease-specific QoL with the AFEQT tool (score range= 0 (worst) to 100) at baseline and at 1 year follow-up. Two anchor-based methods were used to relate changes in AFEQT to clinically important differences in the more established European Heart Rhythm Association (EHRA) measure of functional status. Ranging from 1 (no symptoms) to 4 (disabling), a change of 1 EHRA class was defined as an important change in the anchor. Both the mean change and receiver operating characteristics (ROC) methods were then used to identify CIDs in AFEQT at 1 year follow-up. This was done for both improvement and worsening on the anchor. The mean change method defines a CID as the mean change in AFEQT score among patients with a 1 EHRA class change. The ROC method identifies a CID as the point on the ROC curve that best discriminates patients who experienced an important change in the anchor (≥ 1 EHRA class change) from those who experienced no change.Results: AFEQT was assessed in 2008 AF patients at baseline and 1347 patients at 1 year from 99 US sites participating in ORBIT-AF. CIDs and 95% confidence intervals (CI) corresponding to an improvement in EHRA for the mean change method were 5.4 (3.6, 7.2) AFEQT points and 1.9 (0.4, 9.3) AFEQT points for the ROC method. CIDs corresponding to worsening in EHRA for the mean change method were -4.2 (-6.9,-1.5) AFEQT points and -7.4 (-13.9,-4.6) AFEQT points for the ROC method.Conclusions: Changes in AFEQT as small as 2 points may be clinically relevant, although CIDs vary depending on the method of calculation. The variability suggests identifying a single universal CID to assess improvement in quality of life in AF patients may not be ideal and improvement may relate to the nature of a patient’s symptoms and their baseline level of activity.