To screen out specific VOCs associated with GERD and different phenotypes of GERD and further evaluate their value in the diagnosis of GERD.

The study subjects were grouped based on endoscopic findings and esophageal 24 h pH monitoring results . Breath specimens from GERD patients and healthy control patients were collected, and VOCs in the samples were analyzed by combined SPEM/GC-MS technique, and VOCs markers of GERD and GERD subtypes were screened by comparison with MPP software, and their value in the diagnosis of GERD was evaluated by ROC curve.

There were significant differences in body weight and BMI between different subtypes of GERD and control group (P＜0.05), but no difference in age (P＞0.05);Four VOCs with significant differences, including n-dodecane, n-hexadecane, 5-methyl-undecane and 5-ethyldecane, were screened in GERD compared with the control group. N-tetradecane, n-hexadecane, 5-methyl-undecane and 5-propylnonane were screened in EE+pH⁺ group. O-trifluoromethylbenzoic acid, 2-methyl-undecane and n-dodecane, were screened in NERD. 5-methyl-undecane, 5-ethyl-decane and 5-propyl-nonane were screened in EE+pH^-. By making ROC curves, we found that the sensitivity of 5-ethyl-decane for the diagnosis of GERD was 80.90%, specificity 47.61% (P＞0.05), but no reference value. 5-methyl-undecane had 88.40% sensitivity and 48.40% specificity. The sensitivity of n-dodecane was 91.20% and the specificity was 53.85%. The sensitivity of n-hexadecane was 91.20% and the specificity was 53.86%.

5-methyl-undecane, n-dodecane and n-hexadecane can be used as landmark VOCs for early discri mination between GERD patients and healthy populations, among which n-dodecane may serve as a new reference indicator for early diagnosis of GERD.