Highlights
1) In the article we have evaluated the promoter methylation levels of two CpG islands containing 31 loci in ERAP1 gene. The methylation levels of ERAP1_1 (P < 0.001) and ERAP1_2 (P < 0.001) islands were significantly hypermethylated in AS patients compared with healthy controls.
2) Correspondingly, the mRNA level of EARAP1 was significantly lower in AS patients.
3) The ROC curve analysis also reported that the sensitivity, specificity and area under curve were 0.717, 0.737 and 0.779 of 15 differential methylated CpG loci of ERAP1 for AS diagnosis.
4) Besides, we also found that the methylation level was associated with the family history, non-steroidal anti-inflammatory drugs use, X-ray classification and clinical manifestations of AS.