Digital biomarkers for Duchenne muscular dystrophy
The condition in which a wearable derived measure first reached primary endpoint status with a European regulator.
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Duchenne muscular dystrophy holds a specific place in this library. It is the condition in which a wearable derived measure first reached primary endpoint status with a European regulator, and that decision has shaped how digital measurement is discussed across every other condition since.
The measure is stride velocity 95th centile, which describes the fastest walking a person achieves in ordinary life rather than their average. In 2023 the European Medicines Agency issued a qualification opinion supporting its use as a primary endpoint in ambulatory Duchenne muscular dystrophy. Alongside it, this category collects the broader mobility measures used in the condition, including daily step count, walking bout structure and gait speed.
The reasons this condition led the field are worth understanding, because they explain why the precedent has not transferred automatically elsewhere. Duchenne is progressive and relatively predictable, the population is young and highly monitored, trials are small enough that endpoint sensitivity has real consequences, and conventional functional tests depend on effort and cooperation in a way that continuous measurement does not.
Digital biomarkers used in Duchenne muscular dystrophy research
How these measures are used
The central use is measuring decline in ambulatory function with enough sensitivity to detect a treatment effect in a small population. Conventional timed function tests require maximum effort on demand, which is difficult to obtain consistently from children and adolescents and which introduces variability unrelated to disease.
Continuous measurement addresses that directly. A measure derived from thousands of strides across several weeks is less sensitive to whether a participant was cooperative on the day of assessment, and the 95th centile of stride velocity specifically captures best performance without requiring anyone to be asked to perform.
Digital measures in this condition are used together with the established functional scales rather than instead of them. The regulatory qualification supports use as a primary endpoint in defined circumstances, not a wholesale replacement of the existing assessment framework, and trials continue to report the conventional tests alongside.
What the evidence supports today
This category contains the strongest regulatory precedent in the library. The European Medicines Agency qualification opinion on stride velocity 95th centile in 2023 made it the first wearable derived measure accepted as a primary endpoint in Europe, following a formal qualification process rather than a single trial submission.
That precedent is specific rather than general. It applies to a defined population, ambulatory patients with Duchenne muscular dystrophy from around four years of age, measured with a specified device and processing pipeline. It is not a general endorsement of wearable gait measurement, and citing it as though it were is a common overreach in this field.
The broader mobility measures in Duchenne have supporting evidence from the same literature that underpins the mobility domain generally, with the important qualification that gait in this condition is atypical and progressively so. Algorithms validated in adult or older adult populations should not be assumed to transfer without population specific verification.
Common questions
What is stride velocity 95th centile?
The walking speed a person reaches at the 95th centile of their stride distribution over a recording period, meaning their fastest ordinary walking rather than their average. It is measured continuously with an ankle worn sensor, so it captures best performance without requiring the person to be asked to perform on demand.
Why does the EMA qualification matter beyond this condition?
Because it established that a wearable derived measure can complete a formal regulatory qualification process and be accepted as a primary endpoint. That is a procedural precedent the whole field references. It does not mean other wearable measures inherit the same status, since the qualification is specific to this measure, population and method.
Do digital measures replace timed function tests in Duchenne trials?
Not entirely. The qualification supports use as a primary endpoint in defined circumstances, and trials generally continue to report established functional scales alongside. The digital measure adds sensitivity and removes dependence on effort on the day; the conventional tests supply continuity with the existing evidence base.
Why did this condition lead the field?
Because the conditions aligned. Progression is relatively predictable, trial populations are small so endpoint sensitivity matters a great deal, participants are young and conventional tests depend heavily on cooperation, and the community and regulators engaged with the qualification process directly.
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