Dramatic elevation in urinary amino terminal titin fragment excretion quantified by immunoassay in Duchenne muscular dystrophy patients and in dystrophin deficient rodents.

•New immunoassays were developed for quantification of amino-terminal fragments of titin in urine.•A 365-fold increase in urinary titin concentration was seen in DMD patient urine over controls.•Similar increases in urinary titin were seen in mdx mice and Dmdmdx rats over controls.•Urinary titin was significantly correlated with serum CK and serum skeletal muscle TnI in mdx mice.•Urinary N-ter titin has potential as a non-invasive DMD biomarker.