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Evaluation of functional outcome measures as a surrogate marker of disease severity in patients with mitochondrial disease

Newman, J., Galna, B.ORCID: 0000-0002-5890-1894, Jakovljevic, D., Bates, M., Schaefer, A., McFarland, R., Turnbull, D., Trenell, M., Rochester, L. and Gorman, G. (2013) Evaluation of functional outcome measures as a surrogate marker of disease severity in patients with mitochondrial disease. Journal of Neurology, Neurosurgery & Psychiatry, 84 (11). e2.

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Mitochondrial diseases are a heterogeneous group of genetic disorders, resulting in significant morbidity and disability. The molecular basis of many of the common mitochondrial disorders has been elucidated over the last decade; yet currently there are no known cures and few effective treatments. This is compounded by the paucity of natural history studies and the lack of uniformity and relevance of outcome measures in therapeutic trials, research and clinical settings, in this patient population. Functional outcome measures have proven reliable measures to monitor natural history and interventions in other neurological conditions. We sought to evaluate the usefulness of validated functional outcome measures for patients with mitochondrial disease.

Twenty–four patients and 12 sedentary controls were recruited to this case control observational study. This included the six minute timed walk (6MTW), 10 meter walk test (10MWT), Timed up and Go (TUG) and the 5 times sit to stand (5XSTS). These functional measures were compared to clinical measures of peak exercise capacity, proximal muscle strength and disease burden.

All clinical measures used detected significant differences between patients and sedentary controls. Disease severity correlated with TUG (r=0.63, p=.02) and 10MTW (r=0.62, p=.001). Receiver Operating Curve analysis revealed 5XSTS to be the most responsive measure.

The 10 MTW, 6 MTW, TUG and 5 XSTS are valid evaluative outcome measures in patients with mitochondrial disease. The 5XSTS can be used to discriminate between mitochondrial and sedentary controls with high accuracy and 10 MTW and TUG may serve as useful surrogate markers of disease severity.

Item Type: Journal Article
Publisher: BMJ Publishing Group Limited
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