2, similar to fresh phase 1 samples) could be isolated from approximately 85% of the extracted biobank samples (64 from EPIC-Italy and 50 from NSHDS) (Table 2), with no observable systematic effect of storage time (results not shown).
Cohort n Percent RIN RIN (average RNA yield (mean > 6 [+ or -] SD) [+ or -] SD) EPIC-Italy 64 95 7.1 [+ or -] 0.7 3.9 [+ or -] 1.7 NSHDS 50 92 7.4 [+ or -] 0.9 12.2 [+ or -] 7.5 The EPIC-Italy sample set included six samples stored at -80[degrees]C with a RIN of 6.8 [+ or -] 0.5 and RNA yield of 5.1 [+ or -] 1.2.
ANOVA across these samples showed only 14 and 76 genes for EPIC-Italy and NSHDS, respectively, (of a total of 29,662) to vary significantly (p < 0.0033) according to storage time; however, the FDR level was around 100%, meaning that these were most likely false positives.
DNA isolated from 42 EPIC-Italy and 38 NSHDS biobank samples was of good quality (260/280 optical density ratio, 1.75-1.85; molecular weight > 40,000 kD) and yields were comparable with those obtained with fresh material.
Although PCA of 31 samples from each biobank, stored for 13-17 years, showed some scatter [e.g., for samples collected in 1997 in EPIC-Italy and 1996 in NSHDS (13 and 14 years in storage, respectively)], no systematic trend was evident in relation to the storage time (Figure 2C,D).