Table 1

Cross-sectional cTnI levels, per cent ejection fraction and cystatin C levels of asymptomatic subjects with DMD demonstrating elevations from normal level of 0.02 ng/mL (ELISA assay; Siemens Dimension Analyzer, Siemens Laboratory Diagnostics, Tarrytown, New York) and no relation to age, systolic function or kidney function

Age (years)	Serum cTnI (ng/mL)	Per cent ejection fraction	Cystatin C level (mg/L)
8	0.04	57	0.66
9	0.04	60	0.65
10	0.02	45	0.63
10	0.07	64	0.7
10	0.02	51	0.53
10	0.02	52	0.75
11	0.06	58	0.82
12	0.02	60	0.49
15	0.88	50	0.87
15	0.02	64	0.55
17	0.02	58	0.55
17	0.07	63	0.44
18	0.01	59	0.45
19	0.05	49	0.65
19	0.72	48	0.6
24	0.07	39	0.79

Cystatin C normal range: 0.05–1 mg/L.
cTnI, cardiac troponin I; DMD, Duchenne muscular dystrophy.