Reliability of the new freezing of gait questionnaire: Agreement between patients with Parkinson's disease and their carers
Introduction
Freezing of gait (FOG) has recently been defined as an episodic inability to generate effective stepping in the absence of any known cause other than Parkinsonism or high level gait disorders [1]. FOG is a very disabling motor symptom of advanced Parkinson's disease (PD) [2], [3], [4] with a significant impact on fall risk [5] and quality of life [6]. Accurate detection and rating of both the severity and impact of FOG is therefore important [7], [8].
A gold standard measure of FOG is presently lacking. Its unpredictable presentation and sensitivity to medication, cues and heightened attention make it hard to trigger FOG in a clinic or research laboratory [1]. High false negative rates are likely even during the off-phase and when using specially designed gait trajectories [7]. Activity monitoring to measure FOG has shown promising results during standardized test situations in off[8], but high false positive rates may occur in the home situation. Therefore, a questionnaire has a crucial role to play in the measurement and detection of FOG.
Giladi et al. [9] developed the freezing of gait questionnaire (FOG-Q), a six-item scale (range 0–24) consisting of four items which assess FOG severity and two items which assess gait difficulties in general. The FOG-Q has satisfactory test-retest reliability, internal consistency and moderately high correlations with UPDRS-motor and ADL-scores [9], [10]. Its acknowledged drawback, however, is the inclusion of general gait items, thereby reducing its FOG-specificity [10]. The recently revised MDS-UPDRS [11] includes two items on FOG (items 2.13 and 3.11). However, scoring options are based on more than one dimension, confounding an evaluation of FOG features in isolation.
Detection of FOG in the early stages of PD may be difficult when combined with other symptoms and the fluctuating effects of medication. Rating the severity of FOG may be difficult with disease progression because individuals become desensitized to the symptom. For example, FOG presents itself in various subtypes, i.e. with and without dysrhythmic leg movements [7], [12], making it hard to differentiate FOG from turning difficulties [13] and off-state akinesia. This highlights the need for more explanation or even demonstration during evaluation [10]. Detection of the symptom and standardization of severity through real life examples on video may therefore improve the ability to recognize and rate FOG and enhance the accuracy of a questionnaire-based methodology. Accurate perception of FOG is particularly crucial in patients with cognitive impairment [14], [15]. Hence, an around-the-clock carer observation may provide a reliable substitution or supplement to the rating of FOG.
In this study the outlined limitations of the FOG-Q were addressed by developing a new freezing of gait questionnaire (NFOG-Q) largely based on the previous version. An initial item (part I) was added to allow FOG detection and exclusion of patients without the symptom from the actual scoring of FOG severity and impact (parts II and III). A short video segment was appended to clarify different types and durations of FOG. The present study investigated the hypotheses: (1) that a FOG-video would improve the reliability of detecting and rating FOG severity and impact and (2) that there would be high agreement between patients and carers in detecting and rating FOG severity and impact. The structure of the scale and the correlation with other disease characteristics were also explored as part of construct and criterion validity.
Section snippets
Methods
One hundred and two patients and their carers participated in the study from three different medical centers: N = 23, Tel-Aviv Sourasky Medical Centre (Israel); N = 40, University Hospital Leuven (Belgium); N = 39, Northumbria University (United Kingdom). Consecutive patients were recruited during out-patient visits over a period of 9 months, who fulfilled the following inclusion criteria: diagnosis of PD by a consultant neurologist using the Brain Bank criteria [16], a mini mental state exam (MMSE)
Results
One hundred and two patients and their carers participated in the study. Carers were comprised of: 86% spouses; 4% other family members; 4% distant relatives; 6% professional caregivers or nurses. Mean hours per day in the same house with the patient was 19.7 ± 6.82. Some degree of physical assistance was provided by 68% of carers. Carers consisted of a significantly higher proportion of females (see Table 1), but patients and carers did not differ for age and cognition (MMSE-score). Ten patients
Discussion
This study has shown the reliability of the new freezing of gait questionnaire by direct comparison of the ratings of non-demented patients with PD and their carers. Watching a teaching video altered the recognition of FOG in 4/102 patients and 9/102 carers. This suggests that patients’ self-detection may be more reliable than observation by a lay-person. However, as the true occurrence of FOG was unknown, alternative explanations may also apply. For instance, patients themselves may not have
Conflict of interest statement
The authors report no conflict of interest.
Acknowledgements
We thank all the subjects who participated in the study. Thanks are also due to Dr. Katherine Baker, who participated in the data collection and Dr. Steffen Fieuws for his valuable statistical advice. No grant or other financial support was granted to conduct this study.
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