A Self-administered Version of the Functioning Assessment Short Test for Use in Population-based Studies: A Pilot Study

BACKGROUND: The Functioning Assessment Short Test (FAST) is an interviewer-administered scale assessing functional impairment originally developed for psychiatric patients. OBJECTIVES: To adapt the FAST for the general population, we developed a self-administered version of the scale and assessed its properties in a pilot study. METHODS: The original FAST scale was translated into German via forward and backward translation. Afterwards, we adjusted the scale for self-administered application and inquired participants from two ongoing studies in Germany, ‘STAAB’ (Würzburg) and ‘BiDirect’ (Münster), both recruiting subjects from the general population across a wide age range (STAAB: 30-79 years, BiDirect: 35-65 years). To assess reliability, agreement of self-assessment with proxy-assessment by partners was measured via intraclass correlation coefficient (ICC) over the FAST score. Construct validity was estimated by conducting correlations with validated scales of depression (PHQ-9), anxiety (GAD-7), and health-related quality of life (SF-12) and regression analyses using these scales besides potentially disabling comorbidities (e.g. Chronic Back Pain (CBP)). RESULTS: Participants (n=54) had a median age of 57.0 years (quartiles: 49.8, 65.3), 46.3% were female. Reliability was moderate: ICC 0.50 (95% CI 0.46-0.54). The FAST score significantly correlated with PHQ-9, GAD-7, and the mental sub-scale of SF-12. In univariable linear regression, all three scales and chronic back pain explained variance of the FAST score. In multivariable analysis, only CBP and the SF-12 remained significant predictors. CONCLUSION: The German self-administered version of the FAST yielded moderate psychometric properties in this pilot study, indicating its applicability to assess functional impairment in the general population.