Table 1.

Suitability of RNA detection methods for quantification of EV-RNA.

Method	Lower detection limit	RNA vs. DNA specific?	Remarks
Nanodrop spectrophotometer family (Nanodrop, Thermo Fisher Scientific)	3 µg µl–1 to 2 ng µl–1 range for microliter volumes of RNA	No	Not generally suited for measuring EV-RNA due to high lower limit for detection.
Qubit RNA HS (high sensitivity) assay (Thermo Fisher Scientific)	>0.2 ng µl–1 (initial sample concentration if using the maximum volume for the kit, 20 µl of sample)	Yes	Not generally suited for measuring EV-RNA due to high lower limit for detection.
Bioanalyzer Pico chip (Agilent Technologies)	50 pg µl–1	No	Most sensitive quantification method for total RNA, but prone to error. Most relevant for assessing total RNA content and length distribution.
Bioanalyzer small RNA chip (Agilent Technologies)	50 pg µl–1 of purified miRNA or 10 ng µl–1 of total (cell) RNA in size range of 6–150 nt	No	Similar properties as Pico chip. Useful for resolving miRNA from tRNA and other small RNA species.
Quant-iT RiboGreen RNA Assay kit (Thermo Fisher Scientific)	Detection range of 1–200 ng (sample diluted to 1 ml)	No	Less sensitive to contaminants, such as protein and phenol chloroform.
Quantitative reverse transcription polymerase chain reaction (RT-qPCR)	1 fg (~2500 copies for mRNA) of a particular transcript	No	Most sensitive quantification method overall but does not analyse total RNA, must select primers specific to target transcript(s) and validate to check for off-target amplification.