Key result
Molecular testing showed 90.9% sensitivity for Duchenne muscular dystrophy, while mobility status showed 99.3% specificity, demonstrating that individual clinical measures are inconsistent for accurate phenotype classification.
Why the study?
Does a multi-variable approach using mobility status, molecular testing, and age of onset accurately classify Duchenne and Becker muscular dystrophy phenotypes?
Observational (n=987)
Yes
Does a multi-variable approach using mobility status, molecular testing, and age of onset accurately classify Duchenne and Becker muscular dystrophy phenotypes?
Mobility status, molecular test results, and age at symptom onset are important but inconsistent measures for accurately classifying individuals into DMD or BMD phenotypes.
Single measures should not guide DMD/BMD classification; leaves open whether multi-variable models improve accuracy.
Dystrophinopathies are caused by mutations in DMD resulting in progressive muscle weakness. They are historically divided into the more severe Duchenne (DMD) and milder Becker (BMD) muscular dystrophy phenotypes. Classification is important for research and clinical care. The purpose of this study was to describe a multi-variable approach to classifying cases from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) and to assess the accuracy of the diagnostic classification scheme. We used age at loss of mobility, molecular testing results, and age at symptom onset to classify cases as having DMD or BMD and to assess sensitivity and specificity. Mobility status showed low sensitivity and high specificity for predicting DMD (65.5% and 99.3%, respectively) and BMD (62.8% and 97.7%, respectively) phenotypes. Molecular testing showed 90.9% sensitivity and 66.4% specificity for DMD; 76.3% sensitivity and 90.0% specificity for BMD. Age of onset predicted DMD with sensitivity of 73.9% and specificity of 69.0%; BMD had 99.7% specificity and 36.7% sensitivity. Mobility status, molecular test results, and age at symptom onset are important but inconsistent measures for accurately classifying individuals into DMD or BMD phenotypes. These results have implications for prognosis in newly diagnosed individuals and for classifying phenotype in clinical trials.
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Andrews et al. (2018) conducted an observational in Duchenne and Becker Muscular Dystrophy (n=987). Phenotype classification indices (mobility status, molecular testing, age at symptom onset) vs. Reference standard criteria was evaluated on Sensitivity and specificity of clinical indices for predicting DMD and BMD phenotypes. Molecular testing showed 90.9% sensitivity for Duchenne muscular dystrophy, while mobility status showed 99.3% specificity, demonstrating that individual clinical measures are inconsistent for accurate phenotype classification.
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