Journal Article

Determining minimal clinically important differences in the North Star Ambulatory Assessment (NSAA) for patients with Duchenne muscular dystrophy

Mazzone, Elena S., Mayhew, Anna, Hogrel, Jean-Yves, Domingos, Joana, Pitchforth, Jacqueline M., Muntoni, Francesco, Straub, Volker, Selby, Victoria, Mercuri, Eugenio, de Groot, Imelda, Ridout, Deborah, Niks, Erik H., Ayyar Gupta, Vandana, Wolfe, Amy, Rye, Catherine, Chesshyre, Mary, Iodice, Mario, Servais, Laurent, Manzur, Adnan Y., Ricotti, Valeria

2023

Overview

The North Star ambulatory assessment (NSAA) is a functional motor outcome measure in Duchenne muscular dystrophy (DMD), widely used in clinical trials and natural history studies, as well as in clinical practice. However, little has been reported on the minimal clinically important difference (MCID) of the NSAA. The lack of established MCID estimates for NSAA presents challenges in interpreting the significance of the results of this outcome measure in clinical trials, natural history studies and clinical practice. Combining statistical approaches and patient perspectives, this study estimated MCID for NSAA using distribution-based estimates of 1/3 standard deviation (SD) and standard error of measurement (SEM), an anchor-based approach, with six-minute walk distance (6MWD) as the anchor, and evaluation of patient and parent perception using participant-tailored questionnaires. The MCID for NSAA in boys with DMD aged 7 to 10 years based on 1/3 SD ranged from 2.3–2.9 points, and that on SEM ranged from 2.9–3.5 points. Anchored on the 6MWD, the MCID for NSAA was estimated as 3.5 points. When the impact on functional abilities was considered using participant response questionnaires, patients and parent perceived a complete loss of function in a single item or deterioration of function in one to two items of the assessment as an important change. Our study examines MCID estimates for total NSAA scores using multiple approaches, including the impact of patient and parent perspective on within scale changes in items based on complete loss of function and deterioration of function, and provides new insight on evaluation of differences in these widely used outcome measure in DMD.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Age / Ambulatory assessment / Biology and Life Sciences / Care and treatment / Clinical medicine / Clinical trials / Diagnosis / Duchenne muscular dystrophy / Duchenne's muscular dystrophy / Dystrophy / Error analysis / Estimates / Evaluation / Human health sciences / Humans / Male / Medicine and Health Sciences / Minimal Clinically Important Difference / Multidisciplinary / Muscular dystrophy / Muscular Dystrophy, Duchenne / Mutation / Natural history / Patients / Pediatrics / Physical Sciences / Physical Therapy Modalities / Pédiatrie / Questionnaires / Research and Analysis Methods / Sciences de la santé humaine / Standard error / Surveys and Questionnaires / Walking / Walking - physiology