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Table 1 Summary of referenced studies

From: Letter to the editor: blood processing and sample storage have negligible effects on methylation

Ref no. Author Year Sample Anticoagulant Processing DNA extraction Methylation Results
[5] Hebels 2013 Fresh blood Citrate, EDTA, heparin Whole blood stored up to 24 h at room temperature; buffy coat frozen at − 80 °C or in liquid nitrogen QIAamp Blood Mini Kit (QIAGEN) Infinium HumanMethylation450 Bead Chip (Illumina) No significant effect on methylation profiles
[6] Shiwa 2016 Fresh blood EDTA, heparin Whole blood stored at 4 °C for up to 24 h or at − 80° for 7 days Maxwell 16 Blood DNA Purification Kit, QIAGEN Autopure LS, Gentra Puregene Blood Kit, QIAamp DNA Blood Maxi Kit, QIAGEN FlexiGene DNA Kit Infinium HumanMethylation450 Bead Chip (Illumina) Variation in methylation profiles could be corrected by adjusting for cell-type composition
[7] Bulla 2016 Fresh blood EDTA Stored up to 1 year at 4, − 20, and − 80 °C DNeasy Blood and Tissue Kit (QIAGEN) Epitect Methyl II PCR Array “Human Stress and Toxicity” (QIAGEN) Storage conditions had little to no effect on methylation
[8] Huang 2017 Fresh blood Heparin Stored up to 15 days at 24 °C QIAamp Blood Mini Kit (QIAGEN) Pyrosequencing and dot blotting assay (anti-5mC antibody) Methylation altered when sample was stored for longer than 3 days (study did not adjust for differences in cell-type composition)
[9] Staunstrup 2016 Archived dried blood spots N/A Filter cards stored for up to 16 years at − 20 °C DNA extraction according to St Julien et al. (2013), PLoS One [13]. DNA immunoprecipitation coupled with next-generation sequencing and pyrosequencing Methylation profiles from archived samples comparable to fresh material
[10] Soriano-Tarraga 2013 Fresh blood EDTA N/A Autopure LS (QIAGEN), Puregen TM (Gentra Systems), and Chemagic Magnetic Separation Module I (Chemagen) Luminometric Methylation Assay (LUMA) Different DNA extraction methods may introduce some bias in GDM (medians: 78.1%, 76.5%, and 75.1%)
[11] Bundo 2012 Fresh blood Information not available N/A Phenol-chloroform extraction Infinium HumanMethylation450 Bead Chip (Illumina) and pyrosequencing Amplification bias could be greatly reduced by averaging technical replicates