Sources of pre-analytical variations in yield of DNA extracted from blood samples: analysis of 50,000 DNA samples in EPIC.

The European Prospective Investigation into Cancer and nutrition (EPIC) is a long-term, multi-centric prospective study in Europe investigating the relationships between cancer and nutrition. This study has served as a basis for a number of Genome-Wide Association Studies (GWAS) and other types of genetic analyses. Over a period of 5 years, 52,256 EPIC DNA samples have been extracted using an automated DNA extraction platform. Here we have evaluated the pre-analytical factors affecting DNA yield, including anthropometric, epidemiological and technical factors such as center of subject recruitment, age, gender, body-mass index, disease case or control status, tobacco consumption, number of aliquots of buffy coat used for DNA extraction, extraction machine or procedure, DNA quantification method, degree of haemolysis and variations in the timing of sample processing. We show that the largest significant variations in DNA yield were observed with degree of haemolysis and with center of subject recruitment. Age, gender, body-mass index, cancer case or control status and tobacco consumption also significantly impacted DNA yield. Feedback from laboratories which have analyzed DNA with different SNP genotyping technologies demonstrate that the vast majority of samples (approximately 88%) performed adequately in different types of assays. To our knowledge this study is the largest to date to evaluate the sources of pre-analytical variations in DNA extracted from peripheral leucocytes. The results provide a strong evidence-based rationale for standardized recommendations on blood collection and processing protocols for large-scale genetic studies.

Journal Article; Multicenter Study; Research Support, Non-U.S. Gov't;

Funding: The study was funded by European Commission Research & Innovation DG project BBMRI (Biobanking and Biomolecular Resources Research Infrastructure,http://www.bbmri.eu), project number 212111 and by the Regular Budget of International Agency for Research on Cancer (IARC). DNA extraction data used in the study were generated as part of molecular epidemiological studies approved by the Steering Committee of the European Prospective Investigation into Cancer and Nutrition (EPIC, http://epic.iarc.fr). Detailed information about the funding of EPIC is available at http://epic.iarc.fr/funding.php. The funding agencies and organizations which provided funds for DNA extraction in specific EPIC studies were Imperial College London (ICL, BRCD study); Medical Research Council UK (MRC UK, EPHD study); European Community INTERACT project (through MRC Cambridge, UK, INT study, http://www.inter-act.eu); International Agency for Research on Cancer (IARC) and Imperial College London (ICL) (LUND study), EU FP6 Network of Excellence Environmental Cancer Risk, Nutrition and Individual Susceptibility (ECNIS, http:// www.ecnis.org); and Cancer Research UK (CRCUK) (LYMD study).