Assessing differential item functioning for the Social Appearance Anxiety Scale: a Scleroderma atient-centred Intervention Network (SPIN) Cohort Study

Abstract

ObjectivesThe Social Appearance Anxiety Scale (SAAS) is a 16-item questionnaire developed to evaluate fear of appearance-based evaluation by others. The primary objective of this research was to investigate the existence of differential item functioning (DIF) for the 16 SAAS items, comparing patients who completed the SAAS in English and French, either to confirm that scores are comparable or provide guidance on calculating comparable scores. A secondary research objective was to investigate the existence of DIF based on sex and disease status. A tertiary research objective was to assess DIF related to language, sex, and disease status on the recently developed SAAS-5.DesignThis was a cross-sectional analysis using baseline data from patients enrolled in the Scleroderma Patient-centred Intervention Network (SPIN).SettingSPIN patients included in the present study were enrolled at 43 centres in Canada, USA, UK, France and Australia, with questionnaires completed in April 2014 to July 2019.Participants1640 SPIN patients completed the SAAS in French (n=600) or English (n=1040).Primary and secondary measuresThe SAAS was collected along with demographic and disease characteristics.ResultsSix items were identified with statistically significant language-based DIF, four with sex-based DIF and one with disease type-based DIF. However, factor scores before and after accounting for DIF were similar (Pearson correlation >0.99), and individual score differences were small. This was true for both the full and shortened versions of the SAAS.ConclusionSAAS and SAAS-5 scores are comparable across language, sex, and disease-type, despite small differences in how patients respond to some items.

The Scleroderma Patient-centered Intervention Network Self-Management (SPIN-SELF) Program: protocol for a two-arm parallel partially nested randomized controlled feasibility trial with progression to full-scale trial

“…To calculate total scores, the first item (“I feel comfortable with the way I appear to others”) is reverse-coded, all items are summed, and total scores range from 16 to 80, with higher scores indicating greater anxiety. SAAS scores have been validated as a measure of social appearance anxiety for people with SSc through the SPIN Cohort in English and French [ 59 , 60 ].…”

Nationwide and international registries on scleroderma. Past, present, and future

“…The SPIN cohort has furthered the study of physical activity 132 , physical and occupational therapy 133 , hand function 134 , and online self-care intervention in patients with SSc 135 . It has also made advances in the evaluation of mental health in the SSc population, recently also concerning COVID-19 136,137 .…”