Journal Article

Revised Hammersmith Scale for spinal muscular atrophy: A SMA specific clinical outcome assessment tool

Mayhew, Anna, Tennekoon, Gihan, Muntoni, Francesco, Salazar, Rachel, Duong, Tina, Finkel, Richard, Montes, Jacqueline, Pera, Maria Carmela, Day, John, Pane, Marika, Scoto, Mariacristina, Main, Marion, Civitello, Matthew, Mazzone, Elena S., Bushby, Kate, Pasternak, Amy, Dunaway Young, Sally, Gee, Richard, Ramsey, Danielle, Mercuri, Eugenio, Glanzman, Allan M., de Sanctis, Roberto, Quigley, Janet, Mirek, Elizabeth, De Vivo, Darryl, Darras, Basil T.

2017

Overview

Recent translational research developments in Spinal Muscular Atrophy (SMA), outcome measure design and demands from regulatory authorities require that clinical outcome assessments are 'fit for purpose'. An international collaboration (SMA REACH UK, Italian SMA Network and PNCRN USA) undertook an iterative process to address discontinuity in the recorded performance of the Hammersmith Functional Motor Scale Expanded and developed a revised functional scale using Rasch analysis, traditional psychometric techniques and the application of clinical sensibility via expert panels. Specifically, we intended to develop a psychometrically and clinically robust functional clinician rated outcome measure to assess physical abilities in weak SMA type 2 through to strong ambulant SMA type 3 patients. The final scale, the Revised Hammersmith Scale (RHS) for SMA, consisting of 36 items and two timed tests, was piloted in 138 patients with type 2 and 3 SMA in an observational cross-sectional multi-centre study across the three national networks. Rasch analysis demonstrated very good fit of all 36 items to the construct of motor performance, good reliability with a high Person Separation Index PSI 0.98, logical and hierarchical scoring in 27/36 items and excellent targeting with minimal ceiling. The RHS differentiated between clinically different groups: SMA type, World Health Organisation (WHO) categories, ambulatory status, and SMA type combined with ambulatory status (all p < 0.001). Construct and concurrent validity was also confirmed with a strong significant positive correlation with the WHO motor milestones rs = 0.860, p < 0.001. We conclude that the RHS is a psychometrically sound and versatile clinical outcome assessment to test the broad range of physical abilities of patients with type 2 and 3 SMA. Further longitudinal testing of the scale with regards change in scores over 6 and 12 months are required prior to its adoption in clinical trials.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Adolescent / Adult / Analysis / Atrophy / Biology and Life Sciences / Child / Child, Preschool / Children & youth / Childrens health / Clinical outcomes / Clinical trials / Departments / Disease Progression / Female / Hospitals / Humans / Infant / International cooperation / Male / Medical research / Medicine / Medicine and Health Sciences / Middle Aged / Mobility Limitation / Motor Activity / Motor task performance / Muscular dystrophy / Neurology / Neuromuscular diseases / Occupational therapy / Outcome and process assessment (Medical care) / Outcome Assessment, Health Care - methods / Patient outcomes / Patients / People and Places / Physical therapy / Physicians / Pilot Projects / Psychometrics / Quality of life / Rasch model / Research and Analysis Methods / Scholarships & fellowships / Severity of Illness Index / Social Sciences / Spinal Muscular Atrophies of Childhood / Spinal muscular atrophy / Workshops / Young Adult