GC	gastric cancer
CSG	chronic superficial gastritis
CAG	chronic atrophic gastritis
GU	gastric ulcer
GP	gastric polys
CI	confidence interval
CEA	carcinoembryonic antigen
CA19-9	carbohydrate antigen 19-9
CA72-4	carbohydrate antigen 72-4
EGC	early gastric cancer
cfDNA	cell-free DNA
SEPT9	Septin9 gene
mSEPT9	methylated SEPT9
Ct	cycle threshold
BisDNA	bisulfite-modified DNA
qPCR	qualitative assay for real-time polymerase chain reaction
BGD	benign gastric diseases
ROC	receiver operating characteristic curve
AUC	the area under the ROC curve
PPV	positive predictive value
NPV	negative predictive value
CpG	cytosine–guanine dinucleotide