DNA quantity and quality metrics by storage time of specimen.

DNA yield (μg) (measured by Qubit): Extracted DNA concentration was measured using Qubit fluorometer using dsDNA BR Assay Kits from Life Technologies Inc. and total DNA yield for the sample were calculated. A260/280: Absorbance at 260 nm and 280 nm were measured using Nanodrop for extracted DNA from each sample and expressed as a ratio. KapaQC Q129/41 ratio: Kapa Human Genomic DNA Quantification and QC Kit [23] was used to measure the quality of the genomic DNA isolated from these FFPE samples. This ratio is a measure of fragmentation of the genomic DNA extracted from the sample. *CI = confidence Interval. Overall means and standard deviations for quality measures and by storage time, differences per 10 years of storage and 95% confidence intervals estimated by linear regression on continuous time. P-values are for Wald tests of time coefficients in regression models. A slope of zero indicates no association with specimen storage time. P-values are not adjusted for multiple comparisons. $ 1 sample, age group 13–22 years, is missing DNA yield because no DNA remained after the QC step. DNA quantity and quality metrics by storage time of specimen.