Total RNA extraction and quantification
Total RNA was extracted from 50 lL of each liquid
sample and eluted with 30 lL RNase-free water for each
body fluid using the RNeasy Mini Kit (Qiagen Ltd., CA,
USA) following the manufacturer’s protocol. RNase-free
DNase (Qiagen, Hilden, Germany) was added during the
extraction to prevent the contamination of DNA. RNA was
then quantified using the Nanodrop spectrophotometer
(NanoDrop ND-1000 UV spectrophotometer, Thermo
Scientific, Wilmington, USA).