Validity and Reliability of the Persian Version of the Functioning Assessment Short Test in Outpatients With Bipolar Disorder

Some people with bipolar disorder regain psychosocial functioning upon symptomatic remission. The majority still suffer persistent functional difficulties, even though their core affective symptoms are controlled. Functional recovery is considered as important as symptomatic recovery, and assessing functional outcomes is increasingly recommended in clinical and research settings. Therefore, it seems quite necessary to make instruments with acceptable validity and reliability in different languages. A variety of measures are applied to evaluate functional impairments in bipolar disorder studies, but none of them are specifically designed for bipolar disorder. This instrument was developed for clinical evaluation of functional impairments presented by patients suffering from mental disorders (especially bipolar disorder). Functioning Assessment Short Test (FAST) is a brief instrument designed to assess the main functioning problems experienced by psychiatric patients, specifically bipolar patients. Here in this research we examined the psychometric properties of the Persian version of FAST.

This questionnaire development study was conducted in the Psychiatric Department of Imam–Reza Clinic, Shiraz City, Iran. Outpatients diagnosed with bipolar disorder type I and II (n=202) were recruited using convenience sampling. A psychiatrist diagnosed bipolar disorder according to the Diagnostic and Statistical Manual of Mental Disorders (DSM–5). All available information, including psychiatric records, was brought into consideration. Subjects diagnosed with borderline personality disorder, those in the acute phase of bipolar disorder, active drug abusers, and patients with comorbid mental retardation were excluded. The control group consisted of healthy subjects (n=202) recruited using convenience sampling and screened to have no first–degree relatives with bipolar disorder, current psychiatric comorbidity, schizophrenia, or other psychotic disorders. The control group was compared with the patient group regarding sex, age, marital status, and educational level. Based on the results of the Hamilton Depression Rating Scale and the Young Mania Rating Scale scores, patients were classified as euthymic (those with scores < 8) and symptomatic (those with scores ≥ 8). Bipolar disorder patients and the control group were assessed with FAST. The instrument was evaluated regarding face, construct, convergent, discriminant and concurrent validity. The Cronbach alpha and intra–class correlation coefficients were calculated to estimate internal consistency and test–retest reliability, respectively. Data were analyzed using SPSS 23 and Lisrel 22 at a significance level of 0.05.

The control group and patients group had no significant differences regarding sex, age, marital status, and educational level (p>0.05). Face validity for all questions was acceptable with impact scores ≥ 4.9. FAST total scores were higher for the patient group (22.36±14.21) compared to the control group (4.49±2.03; p<0.001). Furthermore, FAST total scores showed a significant difference between the symptomatic and euthymic groups. FAST scores were lower for the euthymic group (13.80±9.06) compared to the symptomatic group (34.89±10.62; p<0.001). The FAST could successfully discriminate between patients and controls as well as euthymic and symptomatic patients. Confirmatory factor analysis also confirmed the selected model (X2/df=5.04; RMSEA=0.101; NFI=0.96; CFI=0.97; IFI=0.97; GFI=0.80). The FAST also showed acceptable convergent and discriminant validity. The findings showed that the scaling success rates for convergent and discriminant validity were 100% for all domains. Total FAST scores were strongly and negatively correlated with the Global Assessment of Functioning scores (rho= –0.9, p<0.001); therefore, FAST showed an acceptable concurrent validity. The Cronbach alpha coefficient and intra–class correlation coefficient in the Persian version of the FAST were above 0.7.

Based on the findings of this study, the Persian version of FAST has sufficient validity and reliability, making it an acceptable assessment for application in clinical trials and comparative studies.