Clinical relevance of salivary pepsin detection in diagnosing gastroesophageal reflux disease subtypes

Background: Gastroesophageal reflux disease (GERD) is heterogeneous with a varied symptom spectrum and reflux profiles. Its definite diagnosis often requires invasive tools including endoscopy or reflux monitoring. The aim of this study was to investigate the clinical relevance of salivary pepsin detection as a non-invasive screening tool to diagnose GERD of different subtypes. Methods: A total of 77 patients with suspected GERD symptoms and 12 asymptomatic controls were analysed. All participants performed symptom evaluation, upper endoscopy, esophageal manometry, and 24-hour multichannel intraluminal impedance-dual pH probe monitoring. Saliva was self-collected across three different time points: at early fasting, postprandially, and at symptom occurrence. Salivary pepsin levels were measured via Peptest. The optimal threshold of salivary pepsin for diagnosing distal or proximal reflux was determined according to a receiver-operating characteristic curve. Results: The average salivary pepsin concentration of suspected GERD patients was significantly higher than that of controls (100.63 [68.46, 141.38] vs 67.90 [31.60, 115.06] ng/mL, P = 0.044), although no difference was found among patients with different symptom spectrums. The distal reflux group had a higher average pepsin concentration than non-reflux patients (170.54 [106.31, 262.76] vs 91.13 [63.35, 127.63] ng/mL, P = 0.043), while no difference was observed between the distal reflux group and the proximal reflux group. The optimal cut-off value of salivary pepsin concentration for diagnosing pathological distal reflux was 157.10 ng/mL, which was higher than that for diagnosing pathological proximal reflux (122.65 ng/mL). The salivary pepsin concentration was significantly correlated with distal and proximal reflux parameters. Conclusions: Salivary pepsin measurement can help in identifying true GERD with pathological distal reflux or proximal reflux, regardless of different symptom spectrums. A higher threshold should be applied for diagnosing distal reflux than for proximal reflux.