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Determining minimal clinically important differences in the Hammersmith Functional Motor Scale Expanded for untreated spinal muscular atrophy patients: An international study

Lookup NU author(s): Dr Anna Mayhew, Robert Muni Lofra, Dr Chiara Marini Bettolo

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

© 2024 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.Background and purpose: Spinal muscular atrophy (SMA) is a rare and progressive neuromuscular disorder with varying severity levels. The aim of the study was to calculate minimal clinically important difference (MCID), minimal detectable change (MDC), and values for the Hammersmith Functional Motor Scale Expanded (HFMSE) in an untreated international SMA cohort. Methods: The study employed two distinct methods. MDC was calculated using distribution-based approaches to consider standard error of measurement and effect size change in a population of 321 patients (176 SMA II and 145 SMA III), allowing for stratification based on age and function. MCID was assessed using anchor-based methods (receiver operating characteristic [ROC] curve analysis and standard error) on 76 patients (52 SMA II and 24 SMA III) for whom the 12-month HFMSE could be anchored to a caregiver-reported clinical perception questionnaire. Results: With both approaches, SMA type II and type III patients had different profiles. The MCID, using ROC analysis, identified optimal cutoff points of −2 for type II and −4 for type III patients, whereas using the standard error we found the optimal cutoff points to be 1.5 for improvement and −3.2 for deterioration. Furthermore, distribution-based methods uncovered varying values across age and functional status subgroups within each SMA type. Conclusions: These results emphasize that the interpretation of a single MCID or MDC value obtained in large cohorts with different functional status needs to be made with caution, especially when these may be used to assess possible responses to new therapies.


Publication metadata

Author(s): Coratti G, Bovis F, Pera MC, Scoto M, Montes J, Pasternak A, Mayhew A, Muni-Lofra R, Duong T, Rohwer A, Dunaway Young S, Civitello M, Salmin F, Mizzoni I, Morando S, Pane M, Albamonte E, D'Amico A, Brolatti N, Sframeli M, Marini-Bettolo C, Sansone VA, Bruno C, Messina S, Bertini E, Baranello G, Day J, Darras BT, De Vivo DC, Hirano M, Muntoni F, Finkel R, Mercuri E

Publication type: Article

Publication status: Published

Journal: European Journal of Neurology

Year: 2024

Pages: epub ahead of print

Online publication date: 24/04/2024

Acceptance date: 04/04/2024

Date deposited: 08/05/2024

ISSN (print): 1351-5101

ISSN (electronic): 1468-1331

Publisher: John Wiley and Sons Inc

URL: https://doi.org/10.1111/ene.16309

DOI: 10.1111/ene.16309


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