Validity and reliability of a new clinician-rated tool for freezing of gait severity

Abstract

Purpose

The Freezing of Gait Severity Tool (FOG Tool) was developed because of limitations in existing assessments. This cross-sectional study investigated its validity and reliability.

Methods

People with Parkinson’s disease (PD) were recruited consecutively from clinics. Those who could not walk eight-metres independently (with or without an assistive device), comprehend instructions, or with co-morbidities affecting walking were excluded. Participants completed a set of assessments including the FOG Tool, Timed Up and Go (TUG), and Freezing of Gait Questionnaire. The FOG Tool was repeated and those reporting no medication state change evaluated for test-retest reliability. Validity and reliability were investigated through Spearman’s correlations and ICC (two-way, random). McNemar’s test was applied to compare the FOG Tool and TUG on the proportion of people with freezing.

Results

Thirty-nine participants were recruited [79.5%(n = 31) male; Median(IQR): age–73.0(9.0) years; disease duration–4.0(5.8) years]. Fifteen (38.5%) contributed to test-retest reliability analyses. The FOG Tool demonstrated strongest associations with the Freezing of Gait Questionnaire (ρ = 0.67, 95%CI 0.43–0.83). Test-retest reliability was excellent (ICC = 0.96, 95%CI 0.88–0.99). The FOG Tool had 6.2 times the odds (95%CI 2.4–20.4, p < 0.001) of triggering freezing compared to the TUG.

Conclusions

The FOG Tool appeared adequately valid and reliable in this small sample of people with PD. It was more successful in triggering freezing than the TUG.

IMPLICATIONS FOR REHABILITATION

• The Freezing of Gait Severity Tool’s assessment course is more effective than the commonly-used Timed Up and Go’s assessment course for eliciting freezing of gait for clinical evaluation in people with Parkinson’s disease.

• The Freezing of Gait Severity Tool can be considered for scoring freezing of gait severity in people with Parkinson’s disease in the clinical setting.

Keywords:

• Parkinson’s disease
• freezing of gait
• assessment
• clinician-rated tool

Acknowledgements

The authors acknowledge Singapore General Hospital’s Department of Physiotherapy, Department of Neurology, and research assistants Ms Sherry Leow and Ms Abigail Koh for their support during data acquisition. The authors also thank undergraduate physiotherapy students Benjamin Lam and Lee Boon Yee for contributing their honours research budget towards this study.

Ethical approval

This study was approved by the ethics committees of the relevant institutions (SingHealth: CIRB 2019/2650, Curtin University: HRE2020-0094).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data supporting the results of this study is not publicly available, but can be obtained from the corresponding author upon reasonable request.

Additional information

Funding

The authors disclosed receipt of the following financial support for the research – Mitsui Sumitomo Insurance Welfare Foundation Research Grant 2020. The funders had no role in the design, conduct, or reporting of this study. AS is supported by an Australian Government Research Training Program (RTP) scholarship.