Plasma RNA integrity analysis: methodology and validation.

The detection of cell-free RNA in plasma and serum of human subjects has found increasing applications in the field of medical diagnostics. However, many questions regarding the biology of circulating RNA remain to be addressed. One issue concerns the molecular nature of these circulating RNA species. We have recently developed a simple and quantitative method to investigate the integrity of plasma RNA. Our results have suggested that cell-free RNA in plasma is generally present as fragmented molecules instead of intact transcripts, with a predominance of 5' fragments. In this article, we summarize the basic principles in the experimental design for plasma RNA integrity analysis and highlight some of the important technical considerations for this type of investigation.