Measurement of skeletal muscle mass in Duchenne muscular dystrophy: use of 24-h creatinine excretion.

Creatinine concentration in 24-h urine has been proposed as an indirect measure of body skeletal muscle mass (SMM). We attempted to correlate urinary creatinine levels with SMM in eight patients with Duchenne muscular dystrophy, a progressive disease in which the degree of muscle wasting parallels the rate of progression. Magnetic resonance imaging and a newly developed protocol for image analysis were used for the measurement of SMM. The patients ate a creatine-free diet for the week before urine collection. Creatinine was measured with an enzymatic-colorimetric method. Mean (+/-SD) SMM value was 5.4+/-2.5 kg and urine creatinine levels 205.8+/-96.4 mg/day. Daily urinary creatinine excretion did not correlate with SMM. The simple creatinine determination in urine cannot predict SMM in Duchenne muscular dystrophy.