Validity and Reliability of the Tunisian Arabic Functioning Assessment Short Test (FAST) and Functional Outcome Factors in a Sample of Patients with Bipolar Disorder

Abstract

Background Bipolar disorders negatively impact functional outcomes and, consequently, prognosis. The Functioning Assessment Short Test is a reliable tool to evaluate functional outcomes in people with bipolar disorders. Aim The aim of the study was to conduct a cross-cultural validation of the Functioning Assessment Short Test (FAST) and to explore correlations between functional impairment and sociodemographic and clinical variables. Methods A cross-sectional study was carried out in a population of 60 bipolar patients and 60 healthy controls. The scales administered were the Global Functioning Assessment (GAF), the World Health Organization Quality Of Life-Bref (WHOQOL-BREF), the FAST, and a questionnaire containing sociodemographic and clinical variables. The validation study was based on face and content validity, reliability, and construct validity. Results The face and content validity were satisfactory. The internal consistency obtained was high, with a Cronbach’s alpha of 0.785. All six FAST domains had significant correlations with each other and with the total score. The FAST assessment at baseline and week 2 were highly correlated ( p >0.05), and the intraclass correlation coefficient was 0.998, indicating high test-retest reliability. The FAST total score was negatively and significantly associated with GAF (rho=-0.788, p <0.001) and WHOQOL-BREF scores, suggesting good concurrent validity. The total FAST scores were significantly lower in controls as compared with bipolar patients ( p <0.001), with a cut-off at 26. Functional impairment was significantly associated with the following variables: low educational level, living alone, early age at onset, number of depressive episodes, and treatment associations (mood stabilizers and antipsychotics). Conclusion The Tunisian Arabic version of the FAST demonstrated satisfactory psychometric properties and could be used to assess specific domains of functional impairment in people living with bipolar disorders and may be instrumental in implementing psychosocial and rehabilitation interventions.