VALIDATION DATA

This scale has good internal consistency , Cronbach's alpha was 0.93. Item-total correlations range was 0.66 to 0.83.

For those patients reporting no change in AS-specific health at 2 weeks (n=323), the ICC was 0.77 (95% confidence interval: 0.72, 0.81). For those reporting no change in general health (n=319), the ICC was 0.78 (95% confidence interval: 0.73, 0.82)

For the original ASES, a rheumatologist generated 23 original items; these items were refined, and an additional 20 items added following 3 focus groups of people with arthritis. 

Initial validation sample of the ASES (n =97) produced a 2-factor solution (other symptoms, function) using 25 items. The replication study (n = 144) produced a 3-factor solution (pain, other symptoms, function) using 20 items. Developers stated that the choice between the 2 and 3 factor solution was arbitrary, and they based the decision on the importance of pain and the performance of the other  symptoms subscale in regard to depression.

For the ASES-8, exploratory factor analysis for the entire sample and in all 12 subgroups demonstrated a one factor solution (factor loadings: 0.61 to 0.89).

The results of comparisons of the ASES-AS with other measures provided acceptable evidence in support of the construct validity of the modified measure.