Reliability and variability of physiotherapists scoring freezing of gait through video analysis.

BACKGROUND: The "gold standard" marker for freezing of gait severity is percentage of time spent with freezing observed through video analysis. OBJECTIVE: This study examined inter- and intra-rater reliability and variability of physiotherapists rating freezing of gait severity through video analysis and explored the effects of experience. METHODS: Thirty physiotherapists rated 14 videos of Timed Up and Go performance by people with Parkinson's and gait freezing. Ten videos were unique, while four were repeated. Freezing frequency, total duration, and percentage of time spent with freezing were computed. Reliability and variability were estimated using ICC (2,1) and mean absolute differences. Between-group differences were calculated with the one-way ANOVA. RESULTS: Inter- and intra-rater reliability ranged from moderate to good (ICC: inter-rater frequency = 0.63, duration = 0.78, percentage = 0.50; intra-rater frequency = 0.84, duration = 0.89, percentage = 0.50). Variability for freezing frequency was two episodes. Inter- and intra-rater variability for total freezing duration was 18.8 and 12.3 seconds, respectively. For percentage of time spent with freezing, this was 15.2% and 13.5%. Physiotherapy experience had no effect. CONCLUSION: Physiotherapists demonstrated sufficient reliability, but variability was large enough to cause changes in severity classifications on existing rating scales. Percentage of time spent with freezing was the least reliable marker, supporting the use of freezing frequency or total duration instead.

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

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. METHODS: 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. RESULTS: 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.

Developing the Freezing of Gait Severity Tool: A Delphi consensus study to determine the content of a clinician-rated assessment for freezing of gait severity.

OBJECTIVES: There is no standardisation of tasks or measures for evaluation of freezing of gait severity in people with Parkinson's disease. This study aimed to develop a clinician-rated tool for freezing of gait severity (i.e. Freezing of Gait Severity Tool), through determining clinicians' ratings of the most important triggering circumstances to be examined and aspects of freezing of gait to be measured. DESIGN: A three-round, web-based Delphi study. PARTICIPANTS: Healthcare professionals, with at least five years' experience in managing freezing of gait in people with Parkinson. MAIN OUTCOME MEASURES: Round 1 required participants (n = 28) to rate items on a 5-point Likert scale, based on priority for inclusion in the Freezing of Gait Severity Tool. In Round 2, participants (n = 18) ranked the items based on priority for inclusion. In Round 3, participants (n = 18) confirmed or rejected the shortlisted items by judging their ability, on a binary scale, to screen for freezing of gait, detect changes in freezing severity, and discriminate between degrees of severity. RESULTS: Participants agreed with the triggering circumstances of turning hesitation, narrow space hesitation, start hesitation, cognitive dual-tasking, and open space hesitation should be assessed; and the aspects of gait freezing to be measured included freezing type, number of freezing episodes during a task, and average duration of freezing episodes. CONCLUSIONS: This study attained a consensus for the items to be included in a clinician-rated tool for freezing of gait severity. Future studies should investigate psychometric properties and clinical feasibility of the Freezing of Gait Severity Tool.

Measurement Properties of Assessments of Freezing of Gait Severity in People With Parkinson Disease: A COSMIN Review.

OBJECTIVE: Parkinson disease (PD) is the second-most common neurodegenerative condition worldwide. Approximately 50% of people with PD experience freezing of gait, a motor symptom associated with falls, disability, and poorer quality of life. Accurate assessment of freezing of gait severity is important for guiding management. The aim of this systematic review was to determine the measurement properties of subjective and objective clinical assessments of freezing of gait severity using the COSMIN methodology to facilitate better outcome measure selection. METHODS: Three databases (MEDLINE, EMBASE, and CINAHL) were searched. The COSMIN Risk of Bias checklist was used for evaluating quality of included studies. Data on measurement properties were extracted. Where possible, meta-analysis was performed. RESULTS: Nineteen studies investigating measurement properties of 7 outcome measures (patient-reported outcome measures, n = 3; objective assessment tools, n = 4) were included. Ten studies evaluated the Freezing of Gait Questionnaire. Based on COSMIN criteria, the best performing outcome measures were the Freezing of Gait Questionnaire and the Dynamic Parkinson Gait Scale. Both outcome measures demonstrated sufficient structural validity, internal consistency, reliability, construct validity, and responsiveness. The Freezing of Gait Questionnaire was supported with mostly moderate to high quality of evidence, but the evidence for the Dynamic Parkinson Gait Scale was of low quality due to inadequate sample size. CONCLUSIONS: Content validity and measurement invariance remain unknown for all outcome measures. The Freezing of Gait Questionnaire is the best measure currently available. Further external validation and reliability studies would strengthen the evidence to support the use of the Dynamic Parkinson Gait Scale. IMPACT: Awareness of limitations of outcome measures facilitates better selection. Without evidence for content validity and measurement invariance, clinicians should consider if their chosen test accurately measures freezing of gait severity and whether it can be applied in populations different to the original study's population. LAY SUMMARY: Accurately assessing freezing of gait severity is important for guiding management of this disabling symptom. The best clinical assessment currently available is one that relies on the self-report of patients.