Circulating microRNAs (miRs/miRNAs) are being used as non-invasive biomarkers 
for diagnosis, prognosis and efficiency of clinical trials. However, to exploit 
their potential it is necessary to improve and standardize their detection. In a 
previous study, we identified two microRNAs, miR-30c and miR-181a, that appear 
to be key regulators of muscular dystrophy. We hypothesized that they could 
represent useful biomarkers of Duchenne and Becker muscular dystrophies (DMD and 
BMD). The objective of this study was to assess the absolute levels of miR-30c 
and miR-181a in sera of DMD and BMD patients using digital PCR (a robust 
technique for precise and direct quantification of small amounts of nucleic 
acids without standard curves and external references), and investigate the 
correlation between miR-30c and miR-181a expressions and several clinical 
parameters. Our results show that the serum levels of miR-30c and miR-181a 
increased 7- and 6-fold respectively in DMD patients (n = 21, 2-14 years, 
ambulant), and 7-fold in BMD patients (n = 5, 9-15 years) compared to controls 
(n = 22, 2-14 years). No association between miRNA levels and age or 
corticosteroid treatment was detected in DMD. However, there was a trend towards 
higher levels of miR-30c in DMD patients with better preserved motor function 
according to various motor scales and timed tests. We demonstrate that digital 
PCR is a useful technique for accurate absolute quantification of microRNAs in 
sera of DMD/BMD patients. We propose miR-30c and miR-181a as reliable serum 
diagnostic biomarkers for DMD and BMD and miR-30c as a potential novel biomarker 
to assess disease severity in DMD.