Time To Navigate (TTN): A practical objective clinical measure for freezing of gait severity in people with Parkinson's disease

Abstract

ObjectivesTo provide an easy-to-use measure, as existing objective assessments for freezing of gait (FOG) severity may be unwieldy for routine clinical practice, this study explored time taken to complete the recently-validated FOG Severity Tool and its components. DesignCross-sectional SettingOutpatient clinics of a tertiary hospital ParticipantsPeople with Parkinson's who could independently ambulate eight-metres, understand instructions, and without co-morbidities affecting gait were consecutively recruited. Thirty-five participants were included [82.9%(n=29)male; Median(IQR): age – 73.0(11.0)years; disease duration – 4.0(4.5)years]. InterventionsNot applicable Main outcome measuresParticipants were assessed with FOG Severity Tool in a test-retest design, with time taken for each component recorded using a stopwatch during video-analysis. Validity of total FOG Severity Tool time, time taken to complete its turning and narrow-space components (i.e., Time To Navigate, TTN), and an adjusted-TTN were examined through correlations with validated FOG severity outcomes. To facilitate clinical interpretation, TTN cutoff was determined using scatterplot smoothing (LOESS) regression whilst minimal important change (MIC) was calculated using predictive modelling. ResultsFOG Severity Tool time, TTN, and adjusted-TTN similarly demonstrated moderate correlations with the FOG Questionnaire and percentage-FOG, and very-high correlations with FOG Severity Tool-Revised. TTN was nonlinearly related to FOG severity, with a positive relationship observed in the first 300-seconds and plateauing after. MIC for TTN was 15.4-seconds reduction in timing (95%CI 3.2 to 28.7). ConclusionsTTN is a feasible, interpretable, and valid test of FOG severity. In busy clinical settings, TTN can provide a viable alternative when use of existing objective FOG measures is (often) unfeasible.