Shortening patient-reported outcome measures through optimal test assembly: application to the Social Appearance Anxiety Scale in the Scleroderma Patient-centered Intervention Network Cohort

OBJECTIVES: The Social Appearance Anxiety Scale (SAAS) is a 16-item measure that assesses social anxiety in situations where appearance is evaluated. The objective was to use optimal test assembly (OTA) methods to develop and validate a short-form SAAS based on objective and reproducible criteria. DESIGN: This study was a cross-sectional analysis of baseline data from adults enrolled in the Scleroderma Patient-centered Intervention Network (SPIN) Cohort. SETTING: Adults in the SPIN Cohort in the present study were enrolled at 28 centres in Canada, the USA and the UK. PARTICIPANTS: The SAAS was administered to 926 adults with scleroderma. PRIMARY AND SECONDARY MEASURES: The SAAS, Brief Fear of Negative Evaluation II (BFNE II), Brief Satisfaction with Appearance Scale (Brief-SWAP), Patient Health Questionnaire-8 (PHQ8) and Social Interaction Anxiety Scale-6 (SIAS-6) were collected, as well as demographic characteristics. RESULTS: OTA methods identified a maximally informative shortened version for each possible form length between 1 and 15 items. The final shortened version was selected based on prespecified criteria for reliability, concurrent validity and statistically equivalent convergent validity with the BFNE II scale. A five-item short version was selected (SAAS-5). The SAAS-5 had a Cronbach's α of 0.95 and had high concurrent validity with the full-length form (r=0.97). The correlation of the SAAS-5 with the BFNE II was 0.66, which was statistically equivalent to that of the full-length form. Furthermore, the correlation of the SAAS-5 with the two subscales of the Brief-SWAP, and the SIAS-6, were statistically equivalent to that of the full-length form. CONCLUSIONS: OTA was an efficient method for shortening the full-length SAAS to create the SAAS-5