MicroRNA profiling from dried blood samples

MicroRNAs (miRNAs) hold great promise as blood-borne and circulating biomarkers for numerous diseases. However, the reliability of such liquid biopsies is particularly impacted by problems associated with the handling of biological liquids in the pre-analytical stage of biomarker processing. Dried blood spots (DBS) and other capillary blood microsampling devices offer a way to circumvent many of these complications. DBS are supposed to be far less sensitive to collection protocols, storage conditions, and transport processes, while offering the possibility for a decentralized sample collection. In addition, DBS are minimally invasive and require very small amounts of blood, thereby facilitating blood collection from small children or patients at risk by blood drawing. Here, we summarize the current state of knowledge about DBS-derived miRNAs. Experimental studies on miRNA from DBS especially emphasize the influence of the adsorptive material and the importance of drying and rehydration protocols. The present studies are, however, difficult to compare as they use different readout-systems, ranging from PCR-based quantification of single miRNAs to next-generation sequencing (NGS) of the entire miRNome. The data underscore the need for procedure standardization and the development of general guidelines on handling and evaluating miRNA biomarkers derived from DBS.