Objective: To determine the clinimetric properties of the direct rating of the Freezing of Gait (FOG) score compared to the off-line rating from video recordings.

Background: FOG is an episodic gait disorder which makes the clinical evaluation a challenge. We have developed the FOG score which was shown to be a reliable tool to detect alterations introduced by various forms of therapy, e.g. DBS or pharmacologic intervention (1,2). It has recently been given a status of “suggested” by the MDS (3). While its development was done from the evaluation of video sequences, for practical considerations such an approach is not appropriate in daily routine. Here, we compare a direct contemporaneous rating of the FOG score with the established off-line rating from video recordings.

Method: FOG scores were performed by patients with PD, and rated by two independent experts before and 45 minutes after a levodopa dose. Eight weeks later randomised video recordings of the FOG scores were re-evaluated by the same raters blinded to patients and medication state. The intra-rater-reliability of the direct ratings, the re-test-reliability between the direct and video rating, and the validity of the direct rating of the FOG score from comparison to the New FOG questionnaire (nFOGq) as well as to the characterizing FOG questionnaire pt II (cFOGq-II) were estimated with correlation statistics.

Results: 67 patients were contacted. 25 (17 male/ 8 female) fulfilled the inclusion criteria and completed both FOG score ratings and the two other questionnaires. Mean disease duration was 9.9±6.4 yrs, average L-DOPA equivalent dose 1258.3±646.7, and mean Montreal Cognitive Assessment 24.3±3.8 points. The inter-rater and re-test reliability of the direct FOG score was high (Kendall τ 0.81–0.89 and 0.76–0.92, p<0.0001). The direct FOG score ratings correlated moderately with the nFOGq (ρ 0.49-0.53; p<0.05) and with the cFOGq-II (ρ 0.43-0.47; p<0.05).

Conclusion: This is the first report on the clinimetric properties of a direct FOG score rating. The stable correlations between the direct ratings of two raters, and between direct and off-line video rating strongly argue for a reliable alternative to the rating of video recordings. The solid association to the self reported measures of FOG extendits validity. Taken together, this data strengthens the further use of the FOG score for clinical practice and for clinical research.

References: 1. Ziegler K, Schroeteler F, Ceballos-Baumann AO, Fietzek UM. A new rating instrument to assess festination and freezing gait in Parkinsonian patients. Mov Disord. 2010 15;25(8):1012–8. 2. Fietzek UM, Zwosta J, Schroeteler FE, Ziegler K, Ceballos-Baumann AO. Levodopa changes the severity of freezing in Parkinson’s disease. Parkinsonism Relat Disord. 2013;19(10):894–6. 3. Bloem BR, Marinus J, Almeida Q, Dibble L, Nieuwboer A, Post B, et al. Measurement instruments to assess posture, gait, and balance in Parkinson’s disease: Critique and recommendations. Mov Disord. 2016 ;31(9):1342–55.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/clinimetric-properties-of-direct-contemporaneous-fog-score-rating/