Biomarkers of disease progression in adolescents and adults with 5q spinal muscular atrophy: a systematic review and meta-analysis

Since the introduction of disease modifying treatments there is an unmet need to identify biomarkers of spinal muscular atrophy (SMA) natural history. We performed a systematic review and meta-analysis to summarize available evidence. We searched MEDLINE, Embase, Cochrane Library and gray literature until February 2021. The primary outcome was biomarkers longitudinal course in adolescents and adults. The secondary outcome was the discrimination of patients from controls. We included 42 records examining 606 patients from 19 population cohorts over a maximum follow-up of 17-years. Lung function and serum biomarkers could not depict disease progression. We identified potential biomarkers of disease activity [SMA functional rating scale, MoviPlate, pinch strength, compound muscle action potential (CMAP), motor unit number estimation (MUNE)] that require further investigation. Data regarding Hammersmith functional motor scale expanded, Revised upper limb module, 6-minute walk test were contradictory impeding any pooled estimate. The pooled analysis regarding our secondary outcome revealed that upper limb CMAP amplitudes and MUNE mean values differed significantly between SMA patients and controls [mean difference -3.63(-6.2, -1.06), -119.74(-153.93, -85.56) respectively]. Given the lack of natural history data on this population, our qualitative synthesis and meta-analysis could provide valuable evidence and identify promising predictive biomarkers requiring further longitudinal examination.