New Freezing of Gait Questionnaire

Abstract

The New Freezing of Gait Questionnaire (NFOG-Q) is a specialized, patient-reported outcome measure developed to assess the frequency and severity of the debilitating motor phenomenon known as Freezing of Gait (FOG). This scale consists of nine items and represents a significant revision and expansion of its predecessor, the six-item FOG-Q, initially developed in 1999. The NFOG-Q is primarily utilized in clinical settings and research involving patients with Parkinson’s Disease (PD).

A key procedural feature of the NFOG-Q is its conditional administration: the full nine-item questionnaire is only administered if the patient provides a positive response to the initial screening question regarding the presence of FOG. Furthermore, to ensure accurate self-reporting, patients who are unsure about the definition of freezing are often directed to review an explanatory video or receive clinical instruction.

Keywords

New Freezing of Gait Questionnaire, NFOG-Q, Freezing of Gait, FOG, Parkinson’s Disease, Mobility, Activities of Daily Living, Assessment, Motor Symptoms.

Authors

Authors of the original FOG-Q (1999): Giladi N, Shabtai H, Simon ES, Biran S, Tal J, Korczyn AD. Author of the revised NFOG-Q (2009): Nieuwboer A. The official Dutch version was established by the KNGF-richtlijn Ziekte van Parkinson (Royal Dutch Society for Physical Therapy Guideline for Parkinson’s Disease) in 2016.

The original PDF explanation form (Toelichtingsformulier) can be downloaded here: NFOG-Q-form.pdf. The original PDF measurement instrument (Meetinstrument) can be downloaded here: NFOG-Q-meetinstr-ZvP.pdf.

Purpose

The primary purpose of the New Freezing of Gait Questionnaire is to provide a reliable and valid subjective measure of the impact of Freezing of Gait on a patient’s daily life and functional mobility. While objective measures (such as laboratory gait analysis) are highly accurate, they are often impractical for routine clinical monitoring.

The NFOG-Q allows clinicians and researchers to quickly gauge the frequency, severity, and specific circumstances under which FOG episodes occur, enabling better monitoring of disease progression and response to therapeutic interventions, particularly those targeting motor fluctuations in Parkinson’s Disease.

Construct

The NFOG-Q measures the psychological and physical construct of Freezing of Gait, which is characterized by sudden, transient episodes of an inability to initiate or continue locomotion. FOG is a complex motor block that typically occurs during gait initiation, turning, or when navigating tight spaces (e.g., doorways).

The scale operationalizes this construct by focusing on the patient’s subjective experience across various situations, including the severity of the freezing episodes and their resulting impact on activities and movement. By expanding the item pool from six to nine, the NFOG-Q specifically aims to capture a broader range of FOG contexts and symptoms, improving the precision of the subjective assessment.

Validity

Numerous studies have investigated the validity of the NFOG-Q, establishing it as a critical tool in PD assessment. The scale demonstrates strong concurrent validity, correlating highly with objective measures of FOG duration and frequency obtained through laboratory gait analysis and wearable sensors.

Furthermore, the NFOG-Q exhibits good construct validity, showing expected correlations with other established measures of motor severity (e.g., the Unified Parkinson’s Disease Rating Scale, UPDRS) and overall quality of life. Its responsiveness to change, particularly following pharmacological interventions or physical therapy, also supports its utility as an outcome measure.

Reliability

The NFOG-Q is recognized for its robust reliability, demonstrating high internal consistency across multiple language adaptations. Studies typically report Cronbach’s alpha values well above the acceptable threshold of 0.70, suggesting that the nine items consistently measure the same underlying construct (FOG severity).

Test-retest reliability is also generally strong, indicating that the scale provides stable results when administered to patients over short periods, assuming the patient’s clinical status remains unchanged. This stability is crucial for using the NFOG-Q in longitudinal clinical trials and long-term monitoring.

Factor Analysis

Factor analytic studies performed on the NFOG-Q have consistently supported its structure as primarily measuring a single, unidimensional factor related to the severity and frequency of Freezing of Gait. While the original FOG-Q sometimes showed minor factor splits, the revised NFOG-Q, with its nine items, strengthens the coherence of the scale.

The single-factor solution confirms that the items, ranging from frequency of freezing to its impact on specific activities, all contribute significantly to the overall FOG score. This unidimensionality simplifies interpretation, allowing clinicians to use the total score as a comprehensive indicator of the patient’s self-reported FOG burden.

Instrument

Test Type: Questionnaire (Self-Reported Outcome Measure)

Format: 9-item scale administered conditionally. Items are typically scored on a 5-point Likert scale (ranging from 0 to 4), where a higher score indicates greater severity and frequency of FOG.

Language Available: English, Dutch (Nederlandse versie), and various other translations due to international use in PD research.

Population Group: Clinical populations diagnosed with movement disorders, primarily Parkinson’s Disease.

Age Group: Adults, Elderly.

Population Details: Individuals experiencing symptoms of Freezing of Gait, often associated with moderate to advanced stages of PD.

Test Methodology: Patient self-administration, though often supervised by a clinician or researcher. The scale begins with a screening question; if the answer is negative (no FOG experienced), the questionnaire stops.

Keywords

Psychometrics, Validity, Reliability, Motor Block, Movement Disorders, Neurodegenerative, KNGF, Gait Assessment, Clinical Trial Outcome, Activities.

Authors

Author ORCID Identifier: Information not provided in the source material.

Affiliation Email addresses: Information not provided in the source material.

Correspondence Address: Correspondence is typically directed to the primary author of the revised scale, Professor Alice Nieuwboer, or her affiliated institution (KU Leuven, Belgium).

Permissions & Fee and Test Year

The NFOG-Q was published in 2009 by Nieuwboer A. The scale is widely used in non-commercial academic and clinical settings, though specific permissions for large-scale commercial use or adaptation should be sought from the primary author or copyright holder. The original FOG-Q was published in 1999 (Giladi et al.), and the Dutch version was standardized in 2016 (KNGF Guideline).

Reference’s

• Giladi N, Shabtai H, Simon ES, Biran S, Tal J, Korczyn AD. (1999). Construction of a questionnaire for the assessment of freezing of gait in Parkinson’s disease. Parkinsonism & Related Disorders, 5(4), 165-170. (Original FOG-Q)
• Nieuwboer A, Rochester L, Herman T, et al. (2009). Reliability of the new freezing of gait questionnaire in Parkinson’s disease. Gait & Posture, 30(4), 460-464. (Introduction and validation of NFOG-Q)
• KNGF-richtlijn Ziekte van Parkinson (2016). Koninklijk Nederlands Genootschap voor Fysiotherapie. (Dutch Guideline for Parkinson’s Disease, standardizing the Dutch version).

Items of the New Freezing of Gait Questionnaire

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

The specific items of the New Freezing of Gait Questionnaire were not provided in the source content. They are contained within the linked measurement instrument document (NFOG-Q-meetinstr-ZvP.pdf).