Factors associated with delayed diagnosis of spinal muscular atrophy in China and changes in diagnostic delay

•Delayed diagnosis is common in spinal muscular atrophy (SMA).•Type I/II SMA patients visited about 2.56 doctors before obtaining an SMA diagnosis.•Type III SMA patients visited about 3.94 doctors before obtaining an SMA diagnosis.•A national register for rare diseases could enhance identification of SMA.•Collaboration networks and neonatal screening could also reduce diagnostic delays. Spinal muscular atrophy (SMA) is a rare neuromuscular disease, which often occurs in childhood. Early SMA treatment may be highly beneficial to SMA patients, their families, and society. However, delayed diagnosis is common. To identify the factors that affect the SMA diagnostic time window, we analyzed disease characteristics, family factors, and medical factors of 205 SMA families. We compared the data with those of our previous cohort to explore the dynamic changes in the diagnostic time window. The median diagnostic time windows for SMA types I, II, and III were 3.38 [interquartile range (IQR): 2.01–4.98], 4.08 (IQR: 2.07–8.17), and 11.37 (IQR: 4.92–24.07) months, respectively. The diagnostic time window in patients who were clinically diagnosed with SMA at their first hospital visit was 49.42% shorter than that in other patients. Type I/II patients visited approximately 2.56 doctors before diagnosis, while type III patients visited approximately 3.94 doctors before diagnosis. The diagnostic time windows for types II and III were 54.67 and 62.10% shorter, respectively, than those in the previous cohort, which is mainly due to improvements in medical capacity. Therefore, with public awareness, increased medical personnel understanding, and increased neonatal screening, the SMA diagnostic time window is expected to further reduce.