Between June 1998 and June 2001, blood samples were collected from a subset of CPS-II Nutrition Cohort participants (21,965 women and 17,411 men), fractionated into serum, plasma, buffy coat, and RBCs, and stored in liquid nitrogen vapor phase at -130°C until needed for analysis. Subsequently, CPS-II Nutrition Cohort participants who did not provide a blood sample were invited to donate a buccal cell sample which was self-collected using the “swish and spit” method as described by Feigelson et al. (15). The sample was mailed to a central biorepository where the cells were collected by centrifugation and placed into long-term storage in liquid nitrogen vapor phase. This effort resulted in the collection of buccal cell samples from 38,180 women and 31,824 men in 2001 and 2002. Thus, we had DNA from buffy coat or buccal cell samples from 109,380 individuals.
