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 |