Objective: To compute the minimum detectable change (MDC) of an automated algorithm derived spiral analysis parameter for quantification of upper limb action tremor.To compute the minimum detectable change (MDC) of an automated algorithm derived spiral analysis parameter for quantification of upper limb action tremor.

Background: We derived a variable (MD, mean deviation) by automated analysis of hand-drawn, pen-on-paper Archimedes spirals as a surrogate measure of tremor amplitude, and validated it with clinical rating scales and accelerometric measures of tremor. As spiral variables maybe useful to longitudinally quantify tremor in the clinic or in clinical trials, we sought to compute the minimum detectable change (MDC) of the spiral derived parameter MD.

Method: We included subjects with dystonic hand tremor (DT) who were part of a randomized clinical trial of botulinum neurotoxin versus placebo in DT. Spiral drawings from 15 participants who received placebo injections as part of the double-blinded study were utilized to compute MDC, after the completion of the trial. We used spirals drawn at baseline and after 6 weeks of placebo injection.  Free hand spirals drawn on paper were scanned and fed into an automated algorithm to compute the mean deviation (MD) using an in-house developed software. MDC was calculated using the formula, MDC=1.96xSDd and expressed as MDC%=MDC*100/Mean_baseline.

Results: Spirals from 14 participants who received placebo were used. The minimum detectable change for spiral analysis using MD values was computed to be 19.9%.

Conclusion: The MDC for automated analysis of pen-on-paper spirals using the MD metric is much lower than reported values for clinical rating scales or transducer based measures such as accelerometry and digitizing tablets.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/minimum-detectable-change-of-an-automated-algorithm-derived-spiral-analysis-parameter/