Quality Control of DNA Extracted from All-Cell Pellets After Cryopreservation for More Than 10 Years

Cryopreserved whole blood, all-cell pellets (ACPs), and buffy coats in biobanks are widely used to obtain DNA for genetic testing. However, there are few studies concerning the quality control of DNA extracted from them. Our research aimed to perform quality control of DNA extracted from ACPs after cryopreservation for >10 years. A total of 1377 ACP samples (separated from 3 mL of whole blood) were retrieved from our biobank, where they had been cryopreserved for 10-15 years. Chemagic STAR was used to extract the DNA. Absorbance at A260, A280, and A230 were measured by spectrophotometry, and integrity was analyzed by agarose gel electrophoresis. The quality thresholds for an Illumina Asian Screening Array (ASA) were yields greater than 0.5 μg, concentration of 25-150 ng/μL, A260/280 ratio of 1.6-2.1, and no degradation fragments in the electrophoresis gel. The median yield of genomic DNA was 54.30 μg (interquartile range [IQR] 35.55-74.64). The median A260/280 and A260/230 ratios were 1.90 (IQR 1.87-1.94) and 1.98 (IQR 1.64-2.41), respectively. In total, 1377 samples (100%) had qualified yields, and 1366 samples (99.20%) had qualified integrity results. Finally, 1328 (96.44%) samples were used for ASA. Of the remaining samples, 34 needed to be repurified, 4 were obtained at an insufficient concentration, and 11 were unqualified for integrity. In addition, we analyzed the influence of hemolysis (90 samples) and clots (102 samples) on the quality of DNA samples. Hemolysis and clotting did not influence yield or integrity, but a significant difference was found in A260/230 compared to normal samples (p < 0.05). Furthermore, the samples (14 samples) with both hemolysis and clots had higher A260/280 (p < 0.05). ACP samples stored for >10 years at -80°C produced DNA with high quality for use in genetic analysis. Hemolysis and clots in the ACPs led to lower purity, but did not significantly affect yield or integrity.