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.