Background: MicroRNAs (miRNA) are expected as useful biomarkers for various diseases.
We studied the pre-analytical factors causing variation in the analysis of miRNA.
Material and Methods: Blood samples were collected from 25 healthy subjects. Plasma and serum
were obtained from the same samples. The levels of miR-451, -16, -126, and -223 were analyzed using
RT-qPCR. Cel-miR-39 was added as a spiked-in control in each sample.
Results: With the exception of miR-451, the levels of the miRNAs in plasma were higher than in serum.
After high-speed centrifugation, the levels of miRNAs were almost equal between plasma and
serum except for miR-451. Membrane filtration with 0.45 µm pore size reduced the levels of plasma
miRNAs. The coagulation accelerators for serum processing did not affect the analysis of miRNA.
The use of fraction containing particles of > 0.45 µm in size showed the inhibitory effect on the analysis
of plasma miR-451. The RNase inhibitor was effective for protecting against the degradation of miRNAs.
Conclusion: Plasma contains factors modifying miRNA profiles. The immediate processing of plasma
with membrane filtration and RNase inhibitor may be a relevant method for achieving the stable analysis