Citation

Hulzinga F, Nieuwboer A, Dijkstra BW, Mancini M, Strouwen C, Bloem BR, Ginis P. Mov. Disord. Clin. Pract. (Hoboken) 2020; 7(2): 199-205.

Affiliation

KU Leuven, Department of Rehabilitation Sciences, Neurorehabilitation Research Group Leuven Belgium.

Copyright

(Copyright © 2020, John Wiley and Sons)

DOI

10.1002/mdc3.12893

PMID

32071940

PMCID

PMC7011794

Abstract

BACKGROUND: Freezing of gait (FOG) is a common gait deficit in Parkinson's disease. The New Freezing of Gait Questionnaire (NFOG-Q) is a widely used and valid tool to quantify freezing of gait severity. However, its test-retest reliability and minimal detectable change remain unknown.

OBJECTIVE: To determine the test-retest reliability and responsiveness of the NFOG-Q.

METHODS: Two groups of freezers, involved in 2 previous rehabilitation trials, completed the NFOG-Q at 2 time points (T1 and T2), separated by a 6-week control period without active intervention. Sample 1 (N = 57) was measured in ON and sample 2 (N = 14) in OFF. We calculated various reliability statistics for the NFOG-Q scores between T1 and T2 as well as correlation coefficients with clinical descriptors to explain the variability between time points.

RESULTS: In sample 1 the NFOG-Q showed modest reliability (intraclass correlation coefficient = 0.68 [0.52-0.80]) without differences between T1 and T2. However, a minimal detectable change of 9.95 (7.90-12.27) points emerged for the total score (range 28 points, relative minimal detectable change of 35.5%). Sample 2 showed largely similar results. We found no associations between cognitive-related or disease severity-related outcomes and variability in NFOG-Q scores.

CONCLUSIONS: We conclude that the NFOG-Q is insufficiently reliable or responsive to detect small effect sizes, as changes need to go beyond 35% to surpass measurement error. Therefore, we warrant caution in using the NFOG-Q as a primary outcome in clinical trials. These results emphasize the need for robust and objective freezing of gait outcome measures.

© 2020 International Parkinson and Movement Disorder Society.

Language: en

Keywords

freezing of gait; minimal detectable change; new freezing of gait questionnaire; reliability