Exploring outcome measures for adults with myotonic dystrophy type 1

Abstract

Myotonic Dystrophy type 1 (DM1) is a multisystem progressive disorder with high heterogeneity. Novel emerging therapies require assessment tools that can effectively assess the effects of an intervention. The Outcome Measures in 5 Myotonic Dystrophy (OMMYD) Consortium has proposed a battery of functional outcome measures (FOM) identified as relevant for clinical trials in DM1. However, due to the variable nature of the disease and a scarcity of resources, there is a lack of systematic research that properly explores the use of these FOM. The current study examined three of these FOM and one extra related to 10 patients’ daily life performance. These are: (1) the ten-meters walk test; (2) the ten-meters walk/run test; (3) the 30-seconds sit and stand test; and, (4) a tri-axial accelerometer. By exploring the reliability, validity and responsiveness of these outcomes, we aimed to establish reference values and standard methodologies that could serve as guidance for clinical trials in DM1. A cohort of DM1 adults 15 screened for the two largest-to-date trials in DM1 (OPTIMSITIC and PHENO-DM1) were examined in relation to a set of pre-specified assessments and disease-burden scores. The results of this thesis supply disease-specific evidence of their validity, reliability and feasibility. The FOM, have shown to be psychometrically robust measures of functionality in DM1 and to be feasible for 20 clinical trials; they can provide a picture of patients’ muscle strength and perceived mobility and participation in life. The accelerometer can objectively quantify joints accelerations when walking at different speeds and summarise a DM1 patient’s habitual physical activity. The final choice of an outcome measure for a clinical trial in DM1 should be guided by disease domain that an intervention 25 is likely to impact on; but, a disease-specific study like this one will reduce the burden of protocol design whilst providing evidence supporting the decision-making process.