Characterizing the journey of Rett syndrome among females in the United States: a real-world evidence study using the Rett syndrome natural history study database

Table 3 Annual change in CSS and MBA scores among females with RTT, overall and stratified by RTT type and age

Clinical severity measures	Overall RTT Cohort	Stratification by RTT type		Stratification by age
	Overall RTT Cohort	Classic RTT	Atypical RTT	Pediatric (< 18 years of age)	Adult (≥ 18 years of age)
	(N = 455)	(N = 412)	(N = 43)	(N = 363)	(N = 92)
Follow-up period, years, mean ± SD [median]	4.1 ± 1.0 [4]	4.1 ± 1.0 [4]	4.1 ± 1.2 [4]	4.1 ± 1.1 [4]	4.2 ± 0.8 [4]
Mean change in CSS per year (95% CI)	0.11 (-0.08, 0.30)	0.12 (-0.07, 0.31)	0.00 (-0.70, 0.69)	0.24 (0.03, 0.44)	-0.39 (-0.83, 0.05)
Mean change in MBA score per year (95% CI)	0.92 (0.50, 1.35)	0.97 (0.53, 1.41)	0.34 (-1.06, 1.75)	1.12 (0.63, 1.60)	0.17 (-0.61, 0.94)

Abbreviations: CI: confidence interval; CSS: Clinical Severity Scale; MBA: Motor Behavioral Assessment; RTT: Rett syndrome; SD: standard deviation