B-184 Purifying High-Quality Genomic DNA From Frozen Blood Samples Stored up to 1.5 Years at -20°C

Background Maintaining DNA integrity in blood samples, from transport to storage to processing, is crucial to the success of downstream applications, especially regarding diagnostic applications. Additionally, due to the invasive nature of collecting blood samples, minimizing resampling to avoid excess patient pain and cost of collection and transportation are important to consider. Having the option to store and maintain portions of blood samples in the freezer enables future retesting without recollection. Since -20°C freezers generally are more affordable, require less energy, and have smaller footprints than -80°C freezers, demonstrating frozen blood stability at -20°C temperatures could decrease sampling burdens for labs with facility constraints. Methods Whole blood was collected into 9mL vacuum tubes (HemaSure-OMXP) from healthy donors. Aliquots of whole blood and buffy coat samples were stored at -20°C and thawed for genomic DNA extractions (QIAamp DNA Blood Mini Kit, Qiagen) at a range of different timepoints; frozen whole blood samples were processed at 0, 49, 141, and 148 days and frozen buffy coat samples were processed at 7, 27, 36, 185, 246, 373, 394, 584, and 604 days. Purified gDNA was quantified with Qubit (Broad Range dsDNA Assay, ThermoFisher) and qualified with Nanodrop One Microvolume UV-Vis Spectrophotometer (ThermoFisher) and TapeStation (Genomic DNA ScreenTape, Agilent Technologies). Results No significant decrease was observed for DNA yield and quality between fresh and frozen whole blood samples. Average DNA yields from 200 μL whole blood were 4.5 ± 2.2 μg and 5.3 ± 1.2 μg for fresh and frozen blood respectively. Average DNA integrity (DIN) was 6.9 ± 0.4 and 7.1 ± 0.3 for fresh and frozen blood respectively. Donor differences in blood samples can help explain the variance in DNA yields reported. No significant decrease was observed for DNA yield and quality in buffy coat samples frozen for longer at -20°C. In total, 84 whole blood and 25 buffy coat samples were processed in this study. Conclusions Although buffy coat samples tended to have higher yields than whole blood, due to the higher amount of white blood cells present, both sample types provided sufficient amounts of gDNA for downstream applications. Freezing blood samples for future testing can be effective at reducing the need for resampling without sacrificing the nucleic acid yield or quality of fresh samples. Additionally, as technological advancements are made for equipment and assays, frozen blood samples can be retested and compared to previous results for improved diagnostic decisions, done without requiring recollection from labs and patients.