Real-time PCR amplification plots of circulating miRNAs. Shown are the amplification plots for miR-16 (blue), miR-24 (black), and the spiked-in miR-Cel-39 (red) measured in mouse serum (A), mouse serum treated with EDTA (B), and mouse plasma collected on EDTA (C). The y-axis represents the relative fluorescence units (RFU) in a semi-log scale. The x-axis represents the cycle at which fluorescence was detected above an automatically determined threshold for the indicated miRNA. EDTA does not change the concentration of miRNAs in plasma.