Figure 3. Effective and consistent detection of miRNA from plasma. Norgen's Plasma/Serum RNA Purification Mini Kit can effectively isolate miRNA from plasma. Circulating miRNA was isolated from 200 L plasma using Norgen's Plasma/Serum RNA Purification Mini Kit, competitor Q's kit and competitor E's kit. Circulating miRNA was isolated from 600 L using competitor A's kit. Stem loop RT-qPCR using primers specific to miR-21 was performed. In brief, 1 microliter of the 15 L RNA purified using Norgen's Plasma/Serum RNA Purification Mini Kit, competitor Q's kit and 3.3 microliters of the 50 L purified RNA using competitor E's kit and competitor A's kit was then subjected to a 20 L reverse transcription using miR-21 stem-loop reverse primer. Three microliters of the reverse transcription was used in a 20 L real-time PCR reaction with primers to detect the human miR-21. Norgen's Plasma/Serum RNA Purification Mini Kit showed the most consistent and the highest recovery of the miR-21 transcripts as compared to the other isolation methods. The recovery of the miRNA from 200 L plasma using Norgen's kit was higher than that recovered from RNA purified from 600 L using competitor A's kit.