Background: Circulating cell-free miRNAs hold great promise as a new class of biomarkers
due to their high stability in body fluids and association with disease stages. However, even using
sensitive and specific methods, technical challenges are associated with miRNA analysis in body fluids.
A major source of variation in plasma and serum is the potential cell-derived miRNA contamination
Objectives: The study aimed to evaluate the effect of the delayed whole blood processing time on the
concentrations of miR-1 and -423-5p.
Methods: Ten blood samples were incubated for 0, 3 and 24 hours at room temperature prior to processing
into plasma. For each time point, hemolysis was assessed in plasma by UV spectrophotometry
at 414nm wavelength (λ414). Circulating levels of miR-1 and -423-5p were measured by RT-qPCR;
miR-23a and -451 were also analyzed as controls.
Results: A significant hemolysis was observed only after 24h (λ414 0.3 ± 0.02, p < 0.001). However,
only small changes in miR-1 and -423-5p levels were observed up to 24h of storage at room temperature
(Ct 31.5 ± 0.5 to 31.8 ± 0.6for miR-1, p = 0.989; and 29.01 ± 0.3 to 29.04 ± 0.3, p = 0.614 for -
423-5p). No correlation was observed between hemolysis and the levels of miR-1 and -423-5p.
Conclusion: Our data indicate that the storage of whole blood samples at room temperature for up to
24h prior to their processing into plasma does not appear to have a significant impact on miR-1 and -