Blood was drawn from a donor pool of approximately 200 consented, apparently healthy adult subjects into PAXgene Blood ccfDNA Tubes (CE-IVD). Tubes were centrifuged within 2 hours of blood collection, and an aliquot was extracted from 400 µl of nucleated cellular fraction for processing. The remaining sample in each tube were stored at 2–8°C, 25°C, 30°C or 37°C for the indicated number of days. DNA was purified from 180 specimens using the QIAsymphony DSP DNA Mini Kit (elution volume: 200 µl) on the QIAsymphony. Medians and the 25th and 75th percentiles are denoted with box plots.
Whole blood from 20 subjects was collected into PAXgene Blood ccfDNA Tubes (CE-IVD), EDTA tubes and blood collection tubes designed for ccfDNA stabilization from 2 other suppliers. Plasma was separated directly after blood draw, after 3 days and after 7 days storage at room temperature (15–25°C). Hemolysis was assessed by measuring plasma free hemoglobin (pfHb) using the Catachem Plasma Free Hemoglobin (PFH) Kit on the Beckman Counter DxC analyzer. Increase in sample hemolysis during sample storage at room temperature was
minimized in the PAXgene Blood ccfDNA Tubes (CE-IVD) compared to the other blood collection tubes. This indicates red blood cell lysis and decreased sample integrity in the alternative blood collection tubes.
After blood is collected into the tube, the ccfDNA remains stable in whole blood for 7 days at 2–30°C or 1 day at 37°C. Change in plasma ccfDNA yield after whole blood sample storage in comparison to plasma separated within 2 hours of blood collection (day 0). Blood was drawn from a donor pool of approximately 200 consented, apparently healthy adult subjects and stored at various temperatures for the indicated number of days followed by tube centrifugation and ccfDNA purification from plasma on the QIAsymphony. The relative ccfDNA yield was calculated as the ratio of the 18S rDNA CT value after sample storage compared to the CT value at day 0. Medians and the 25th and 75th percentiles are denoted with blox plots.
Whole blood was stored in EDTA tubes or PAXgene Blood ccfDNA Tubes (CE-IVD). ccfDNA was extracted from the plasma immediately following blood collection (t0) or after 6 days storage (t6) at room temperature. Eluate (1 µl) was analyzed using the Agilent High Sensitivity DNA Kit. Plasma from EDTA tubes showed an increase in apoptotic gDNA fragments, whereas plasma from PAXgene Blood ccfDNA Tubes (CE-IVD) showed a ccfDNA profile comparable to day 0.