Table 5.

Laboratory methods of studies performing candidate-loci or global methylation studies

Study	Year	Sample analysed	Methylation Analysis Technique	Coverage Level	Blood cell-type Correction
Lepeule et al. [25]	2012	Leukocytes	PCR and Pyrosequencing	9 candidate genes in pathways of interest: CRAT, F3, GCR, ICAM, IFNγ, IL6, iNOS, OGG1, TLR2	Yes (proportion of lymphocytes and neutrophils)
Lange et al. [26]	2012	Leukocytes	PCR and Pyrosequencing	Alu and LINE-1 elements: coverage of 15,000 different Alu elements/genome.	Yes (proportion of lymphocytes)
Wielscher et al. [24]	2015	Serum (Cell-Free DNA)	MSRE Enrichment and qPCR	63 candidate loci (markers from a 450 K DNAm of lung tissue from those with COPD)	N/A (cell-free DNA)

Abbreviations: PCR Polymerase chain reaction, qPCR Quantitative polymerase chain reaction, MSRE Methyl sensitive restriction enzyme