Construct validity of the items on the Stroke Specific Quality of Life (SS-QOL) questionnaire that evaluate the participation component of the International Classification of Functioning, Disability and Health

Purpose: Analyze the construct validity and internal consistency of the Stroke Specific Quality of Life (SS-QOL) items that address the participation component of the ICF as well as analyze the ceiling and floor effects. Methods: One hundred subjects were analyzed: 85 community-dwelling and 15 institutionalized individuals. The analysis of construct validity was performed using classic psychometrics: (1) the comparison of known groups (individuals without restriction to participation vs. those with restriction to participation) using the Mann-Whitney test and (2) convergent validity - correlation between the scores on the SS-QOL items that address participation and the subscale scores of measures used to evaluate the similar constructs and concepts [the Short-Form Health Survey (SF-36), Functional Independence Measure (FIM) and grip strength test]. Spearman's correlation coefficients were calculated for this analysis. Cronbach's was used for the analysis of internal consistency and both the ceiling and floor effects were analyzed. The level of significance for all analyses was =0.05. Results: The a priori hypotheses regarding construct validity were partially demonstrated, as only five of the eight domains exhibited positive moderate to strong correlations (r>0.40) with measures that address constructs similar to those addressed on the SS-QOL questionnaire. The items demonstrated adequate internal consistency and are capable of differentiating individuals with and without restriction to participation. The ceiling and floor effects were considered adequate for the total SS-QOL score, but beyond acceptable standards for some domains. Conclusions: The 26 items of the SS-QOL questionnaire measure a multidimensional construct and therefore do not only address participation. However, the items demonstrated adequate internal consistency and are capable of differentiating individuals with and without restriction to participation.