Table 4.

Reliability and responsiveness of all assessed indices

				qMRI biomarkers			Functional measures			Molecular biomarkers
				T 2	DIXON‐FF	MP‐FF	CSA	MFM	6MWT	SMN2FL	SMNΔ7	SMN2FL/SMNΔ7	SMN protein
SMA Type III
Reliability
Valid N				14	14	9	14	14	14	7	7	7	11
ICC				0.995 (0.989–0.998)	0.999 (0.999–1.0)	0.994 (0.984–0.999)	0.997 (0.994–0.999)	0.989 (0.975–0.996)	0.976 (0.947–0.991)	0.637 (−0.047–0.926)	0.555 (0.392–0.913)	0.805 (0.350–0.962)	0.929 (0.806–0.979)
Realiability				Excellent	Excellent	Excellent	Excellent	Excellent	Excellent	Good	Good	Very good	Excellent
Responsiveness
Valid N				14	14	10	14	14	14	8	8	8	11
SRM				−0.33	0.23	0.66	0.2	0.02	0.37	0.69	0.47	0.38	−0.28
HV
Reliability
Valid N				15	15	14	15	n/a	n/a	n/a	n/a	n/a	n/a
ICC				0.797 (0.551–0.924)	0.991 (0.980–0.997)	0.993 (0.983–0.997)	0.995 (0.989–0.998)
Reliability				Very good	Excellent	Excellent	Excellent

The cases were excluded list‐wise (i.e., in case of a single missing time point, all data from the particular subject were omitted from the analysis). The ICC value is displayed with a 95% confidence interval and a classification based on Fleiss et al. 2003. SRM was calculated from change scores between the last visit and the first visit. 6MWT, 6‐minute walk test; CSA, muscle cross‐sectional area; CI, confidence interval; FF, fat fraction; HV, healthy volunteers; ICC, intraclass correlation coefficient; MFM, Motor function measure; MP‐FF, multi‐peak FF; qMRI, quantitative magnetic resonance imaging; SMA, spinal muscular atrophy; SMN2FL, SMN2 mRNA expression level; SMNΔ7, SMNΔ7 mRNA expression level; SRM, standardized response mean; Valid N, number of subjects included in the analysis.