Cross-cultural translation, validation, and responsiveness of the Pittsburgh Fatigability Scale - Italian version (PFS-I) in a mixed-sample of older adults.

Introduction: Older adults experience fatigue which impacts health-related quality of life. The Pittsburgh Fatigability Scale (PFS) was specifically designed to assess perceived physical and mental fatigability in older adults. The aim of this study was to translate the PFS into Italian (PFS-I) and to investigate its psychometric properties.

Methods: The PFS-I was translated in accordance with international standards. The following properties were evaluated: structural validity, internal consistency, hypotheses testing for construct validity, test-retest reliability using intraclass correlation coefficients (ICC), and minimal clinically important difference (MCID) for responsiveness.

Results: The study included 87 older adults with cardiovascular/respiratory diseases (CVRD), 46 with Parkinson disease (PD), and 67 healthy controls (HC). The PFS-I Physical and Mental subscales scores were significantly different in these populations, with HC reporting the lowest fatigability. Exploratory and confirmatory factor analysis showed a two-factor structure for both subscales, with good internal consistency (Cronbach's alpha: 0.86 and 0.89, respectively). The PFS-I Physical subscale showed weak goodness-of-fit of the confirmatory factor analysis models, whereas the PFS-I Mental subscale was deemed acceptable. Construct validity of the PFS-I was excellent with 75% (18 out of 24) of hypotheses accepted. Test-retest reliability was analyzed in a subset of 23 patients with CVRD and showed excellent results for both the PFS-I Physical and Mental subscales (ICC = 0.93 and 0.92, respectively). MCID ranged between 6 and 7 points for the Physical and 7-9 points for the Mental subscale.

Conclusions: The PFS-I is a valid, reliable, and responsive instrument to assess perceived fatigability for healthy older adults as well as those with CRVD and PD.