Microarray‐Based Identification of Time‐Sensitive miRNAs as Serum Quality Indicators in Liquid Biopsy

Circulating microRNAs (miRNAs) are promising biomarkers and many studies have been reported. However, there are discrepancies between studies due to differences in the inclusion criteria, experimental procedures, and serum/plasma processing conditions. In this study, we aimed to develop a comprehensive set of miRNA markers to assess the serum quality, which fluctuates depending on the storage duration after blood collection. This study was designed to identify circulating miRNAs that were unstable when stored at room temperature (23°C-27°C) for more than 0.5-1 h after centrifugation to separate the serum. The results showed that 17 miRNAs were more than 5% variable in their signals after storage at room temperature for more than 0.5 h. Of these, seven miRNAs were identified whose signals changed significantly by more than 1 in signal level after 1 h of storage at room temperature, showing time-dependent fluctuations in detection levels. These miRNAs were further evaluated between the two clinical sample groups with different preprocessing times. miR-4429 and miR-6511b-5p showed a significant decrease in signals in the sample group with longer processing times. These miRNAs can be used as markers to assess sample quality and reflect the time-dependent storage conditions of clinical samples.