VALIDATION DATA

The EASi-QoL questionnaire is validated and reliable disease-specific for the assessment of QoL in patients with AS/nr-axSpA.

Physical function α = 0.90

Disease activity α = 0.88

Emotional well-being α = 0.91

Social participation α = 0.92

In a systematic review, the pooled Cronbach’s α coefficients scored as high and moderate quality of evidence of these scale was 0.91 (95% CI 0.88 to 0.93).

ICCs calculated for patients indicating no change in AS-specific health at 2 weeks:

Physical function ICC = 0.93

Disease activity ICC = 0.88

Emotional well-being ICC = 0.90

Social participation ICC = 0.90

Very good reliability of moderate quality was found for the EASi-QoL questionnaire in a systematic review (ICC range from 0.88 to 0.935).

The MIC for the EASi-QoL domains was defined as a change of 10% from baseline for the PF domain (sensitivity 66%, specificity 63%); a change of 20% from baseline for the DA domain (sensitivity 70%, specificity 71%); a change of 15% for the EWB domain (sensitivity 62%, specificity 61%) and a change of 25% for the SP domain (sensitivity 67%, specificity 67%).

The 10% minimal important change (MIC) for the EASi-QoL PF domain (score 0-24) relates to a change score of 1 for scores of ≤10 at baseline, 2 for scores of 11-20 and 3 for scores of 21-24.

The 20% MIC for the EASi-QoL DA domain (score 0-16) relates to a change of 1 point for those scores of ≤5 at baseline, 2 points for scores of 6-10, 3 points for scores of 11-15 and 4 points for scores of 16.

The 15% MIC for the EASi-QoL EWB domain (score 0-20) relates to a change of 1 point for scores ≤6 at baseline, 2 points for scores 7-13 and 3 points for scores 14-20.

The 25% MIC for the EASi-QoL SP domain (score 0-20) relates to a change of 1 point for scores of ≤4 at baseline, 2 points for scores 5-8, 3 points for scores 9-12, 4 points for scores 13-16 and 5 points for scores 17-20.

Patient interviews, a literature review, and completion of an individualized measure of AS quality of life during clinic-based and pilot surveys were used to derive questionnaire content.

Classical and modern psychometrics were used to evaluate the questionnaire using data from a large UK-based postal survey of 1000 patients with AS. Confirmatory factor analysis and Rasch analysis were performed. The EASi-QOL questionnaire focuses on four dimensions: physician function, disease activity, emotional well-being, and social participation. 

Two publications chose the exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) models for the EASi-QOL . It showed that the factor loadings were higher than 0.40 and the item-total correlations were ranged from 0.66 to 0.84. Principle component analysis (PCA) was performed in five studies to assess the dimensionality of instruments. A 2-parameter Rasch model confirmed unidimensionality (chi-square fit p = 0.86) with good item discrimination of the RLDQ.