Abstract

Plasma-derived microRNAs (miRNAs) are being used as biomarkers, and have been associated with human liver disease and function including fibrosis, inflammation, and drug-induced liver injury. They may also be biomarkers of the drug metabolism function of the liver. In order for plasma miRNA to function as a clinical biomarker, predictable variability is necessary during processing from whole blood to plasma. The current study evaluated the variability of miRNA in whole blood stored for 0.5, 1, 2, 4, 8, and 12 hours following the blood draw under clinical conditions (room temperature) prior to the separation of the plasma. Four healthy volunteers were recruited. Blood from all subjects was collected twice. MicroRNA-16 (miR-16) and miR-223 were evaluated because many studies have shown them to be reliably present in plasma and useful for normalization. miRNA concentrations were measured by real-time polymerase chain reaction. The coefficient of variability of the cycle threshold values for subjects for miR-223 and miR-16 ranged from ∼3.6 to 6.8% and ∼1.48 to 4.1%, respectively, over the 12-hour incubation. A second blood collection was performed to determine interday variability. The coefficient of variance from the initial blood draw compared with the final blood draw for each subject ranged from 0.42 to 7.9% for miR-16 and 1.7 to 8.3% for miR-223, indicating that these miRNAs have limited interday variability. We conclude that plasma miR-16 or miR-223 concentrations are stable in whole blood at room temperature for up to 12 hours.