Validation of motor and functional scales for the evaluation of adult patients with 5q spinal muscular atrophy

• Published in: European journal of neurology Vol. 29; no. 12; pp. 3666 - 3675
• Main Authors: Vázquez‐Costa, Juan F., Povedano, Mónica, Nascimiento‐Osorio, Andrés E., Moreno Escribano, Antonio, Kapetanovic Garcia, Solange, Dominguez, Raul, Exposito, Jessica M., González, Laura, Marco, Carla, Medina Castillo, Julita, Muelas, Nuria, Natera de Benito, Daniel, Ñungo Garzón, Nancy Carolina, Pitarch Castellano, Inmaculada, Sevilla, Teresa, Hervás, David
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-12-2022; John Wiley and Sons Inc
• Subjects: Adult; adults; Amyotrophic lateral sclerosis; Atrophy; Child; Cohort analysis; cohort study; Evaluation; Human motion; Humans; Muscular Atrophy, Spinal; Neuromuscular diseases; Neuropathies; nusinersen; Original; Outcome Assessment, Health Care; Spinal Muscular Atrophies of Childhood; Spinal muscular atrophy; treatment; Upper Extremity; Validation studies; Validity; treatment; nusinersen; spinal muscular atrophy; cohort study; adults
• ISSN: 1351-5101; 1468-1331
• DOI: 10.1111/ene.15542

Background and purpose
Mos scales currently used to evaluate spinal muscular atrophy (SMA) patients have only been validated in children. The aim of this study was to assess the construct validity and responsiveness of several outcome measures in adult SMA patients.
Methods
Patients older than 15 years and followed up in five referral centres for at least 6 months, between October 2015 and August 2020, with a motor function scale score (Hammersmith Functional Motor Scale Expanded [HFMSE], Revised Upper Limb module [RULM]) were included. Bedside functional scales (Egen Klassification [EK2], Revised Amyotrophic Lateral Sclerosis Functional Rating Scale [ALSFRS‐R]) were also collected when available. Spearman's rho correlations (rs) and Bangdiwala's concordance test (B) were used to evaluate the scales' construct validity. Monthly slopes of change were used to calculate their responsiveness of the scales.
Results
The study included 79 SMA patients, followed up for a mean of 16 months. All scales showed strong correlations with each other (rs > 0.70). A floor effect in motor function scales was found in the weakest patients (HFMSE < 5 and RULM < 10), and a ceiling effect was found in stronger patients (HFMSE > 60 and RULM > 35). The ALSFRS‐R (B = 0.72) showed a strong ability to discriminate between walkers, sitters and non‐sitters, and the HFMSE (B = 0.86) between walkers and sitters. The responsiveness was low overall, although in treated patients a moderate responsiveness was found for the ALSFRS‐R and HFMSE in walkers (0.69 and 0.61, respectively) and for EK2 in sitters (0.65) and non‐sitters (0.60).
Conclusions
This study shows the validity and limitations of the scales most frequently used to assess adult SMA patients. Overall, bedside functional scales showed some advantages over motor scales, although all showed limited responsiveness.