Background: Population-based epidemiological studies of essential and other tremors have need of a rapid yet accurate means to assess tremor, especially mild tremors. Handwriting is often affected by tremor, and a hand-drawn spiral can provide investigators with objective rather than self-reported data. We present a semi-quantitative, ordinal scale to rate hand-drawn spirals. The scale, which includes values for mild tremor, is accompanied by photographic examples of spirals of each rating, providing a visual template for guidance.
Methods: This study, conducted within the framework of a population-based epidemiological study of 5,000 individuals aged 60 and older in Shanghai, asked enrollees to draw an Archimedes spiral with each hand. Spirals were rated using an ordinal scale (0, 0.5, 1, 1.5, 2, and 3). Three raters rated an initial set of 548 spirals. Four raters rated a subsequent set of 200 spirals using a visual template for guidance.
Results: Initial agreement (548 spirals) was good (r values ranged from 0.49 to 0.62, all p<0.001). Subsequent agreement (200 spirals and using visual template) improved (r values ranged from 0.67 to -0.91, all p<0.001).
Discussion: This tool will be useful to researchers who are attempting to rapidly assess action tremor in their field surveys.
Keywords: Essential tremor; epidemiology; rating scale; reliability; spiral.