Assessment of the psychometric properties of the Italian version of the New Freezing of Gait Questionnaire (NFOG-Q-IT) in people with Parkinson disease: a validity and reliability study

Introduction: Freezingof gait (FOG) in Parkinson’s disease (PD) is a challenging clinical symptom to assess, due to its episodic nature. A valid and reliable tool is the New FOG Questionnaire (NFOG-Q) used worldwide to measure FOG symptoms in PD. Objective: The aim of this study was to translate, to culturally adapt, and to test the psychometric characteristics of the Italian version of the NFOG-Q (NFOG-Q-It). Methods: The translation and cultural adaptation was based on ISPOR TCA guidelines to finalize the 9-item NFOG-Q-It. Internal consistency was assessed in 181 Italian PD native speakers who experienced FOG using Cronbach’s alpha. Cross-cultural analysis was tested using the Spearman's correlation between the NFOG-Q-It and the Modified Hoehn-Yahr Scale (M-H&Y). To assess construct validity, correlations among NFOG-Q-It, Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS), Mini-Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA), the Falls Efficacy Scale-International (FES-I), the 6-min Walking Test (6MWT), the Mini Balance Evaluation System Test (Mini-BESTest) and the Short Physical Performance Battery (SPPB) were investigated. Results: The Italian N-FOGQ had high internal consistency (Cronbach’s α = 0.859). Validity analysis showed significant correlations between NFOG-Q-IT total score and M-H&Y scores (r = 0.281 p < 0.001), MDS-UPDRS (r = 0.359 p < 0.001), FES-I (r = 0.230 p = 0.002), Mini BESTest (r = -0.256 p = 0.001) and 6MWT (r = -0.166 p = 0.026). No significant correlations were found with SPPB, MOCA and MMSE. Conclusion: The NFOG-It is a valuable and reliable tool for assessing FOG symptoms, duration and frequency in PD subjects. Results provide the validity of NFOG-Q-It by reproducing and enlarging previous psychometric data.