Singapore Institute of Technology
Physiotherapy Res Intl - 2023 - Scully - Scoring festination and gait freezing in people with Parkinson s The freezing of.pdf (662.76 kB)

Scoring festination and gait freezing in people with Parkinson's: The freezing of gait severity tool‐revised

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posted on 2023-07-28, 07:08 authored by Aileen Eugenia ScullyAileen Eugenia Scully, May Leng Dawn TanMay Leng Dawn Tan, Beatriz Ito Ramos de Oliveira, Keith D. Hill, Ross Clark, Yong Hao Pua

Background and Purpose

To improve existing clinical assessments for freezing of gait (FOG) severity, a new clinician-rated tool which integrates the varied types of freezing (FOG Severity Tool-Revised) was developed. This cross-sectional study investigated its validity and reliability.


People with Parkinson's disease who were able to independently ambulate eight-metres and understand study instructions were consecutively recruited from outpatient clinics of a tertiary hospital. Those with co-morbidities severely affecting gait were excluded. Participants were assessed with the FOG Severity Tool-Revised, three functional performance tests, the FOG Questionnaire, and outcomes measuring anxiety, cognition, and disability. The FOG Severity Tool-Revised was repeated for test-retest reliability. Exploratory factor analysis and Cronbach's alpha were computed for structural validity and internal consistency. Reliability and measurement error were estimated with ICC (two-way, random), standard error of measurement, and smallest detectable change (SDC95). Criterion-related and construct validity were calculated with Spearman's correlations.


Thirty-nine participants were enrolled [79.5% (n = 31) male; Median (IQR): age–73.0 (9.0) years; disease duration–4.0 (5.8) years], with fifteen (38.5%) who reported no medication state change contributing a second assessment for reliability estimation. The FOG Severity Tool-Revised demonstrated sufficient structural validity and internal consistency (α = 0.89–0.93), and adequate criterion-related validity compared to the FOG Questionnaire (ρ = 0.73, 95% CI 0.54–0.85). Test-retest reliability (ICC = 0.96, 95%CI 0.86–0.99) and random measurement error (%SDC95 = 10.4%) was acceptable in this limited sample.

Discussion and Conclusions

The FOG Severity Tool-Revised appeared valid in this initial sample of people with Parkinson's. While its psychometric properties remain to be confirmed in a larger sample, it may be considered for use in the clinical setting.


Mitsui Sumitomo Insurance Welfare Foundation Research Grant 2020


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Physiotherapy Research International

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