Pre-analytical variables in miRNA analysis.

MicroRNAs (miRNAs) are short non-coding RNAs that are involved in the regulation of cellular processes and have been shown to be differentially expressed in neoplasia and other disease states. This renders miRNAs promising diagnostic and prognostic biomarkers in tissues and body fluids, especially in blood. However, numerous variables can influence the detection of miRNAs in the pre-analytical phase and lead to erroneous results. This is of particular concern when miRNA profiles are used clinically and alter diagnosis and patient treatment. Since miRNAs have been discovered relatively recently, systematic studies examining pre-analytical variables are rare. Therefore, this review comprehensively summarizes the current knowledge of pre-analytical variables that influence miRNA analysis in general, as well as pre-analytical variables that are specific to the detection of circulating miRNAs and tissue miRNAs.