The New Freezing of Gait Questionnaire: Unsuitable as an Outcome in Clinical Trials?

Femke Hulzinga, Alice Nieuwboer, Bauke W. Dijkstra, Martina Mancini, Carolien Strouwen, Bastiaan R. Bloem, Pieter Ginis

Research output: Contribution to journalArticle

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.

Original languageEnglish (US)
Pages (from-to)199-205
Number of pages7
JournalMovement Disorders Clinical Practice
Volume7
Issue number2
DOIs
StatePublished - Feb 1 2020

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Keywords

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

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

Cite this

Hulzinga, F., Nieuwboer, A., Dijkstra, B. W., Mancini, M., Strouwen, C., Bloem, B. R., & Ginis, P. (2020). The New Freezing of Gait Questionnaire: Unsuitable as an Outcome in Clinical Trials? Movement Disorders Clinical Practice, 7(2), 199-205. https://doi.org/10.1002/mdc3.12893