Accuracy and Clinical Findings of Saliva Digestive Biomarkers in Laryngopharyngeal Reflux Disease

Introduction: Salivary pepsin has served as the primary diagnostic biomarker for laryngopharyngeal reflux disease (LPRD). To date, the diagnostic accuracy of other digestive enzymes in saliva remains largely unexplored.

Objective: To evaluate the diagnostic performance of multiple digestive enzyme biomarkers in detecting and characterizing LPRD.

Methods: Patients with LPRD at the 24-hour hypopharyngeal-esophageal multichannel intraluminal impedance-pH testing (HEMII-pH) were consecutively recruited from January 2020 to May 2024 from two European Hospitals. The control group consisted of adults without symptoms.Prospective clinical data collection included demographics, gastrointestinal endoscopy, HEMII-pH, reflux symptom score (RSS), and reflux sign assessment (RSA) findings. At baseline, pepsin, elastase, cholesterol, bile acids, trypsin, pancreatic and gastric lipase were measured in saliva samples of LPRD patients and asymptomatic individuals. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy (receiver operating characteristic (ROC) curve and area under the curve (AUC)) were evaluated.

Results: One hundred and twenty-three patients and forty-eight asymptomatic individuals were prospectively recruited. Patients exhibited significantly elevated salivary pH and elastase levels, but decreased cholesterol compared to controls. Salivary cholesterol demonstrated superior diagnostic performance (AUC=0.989), with a 2.05 mg/dL threshold yielding excellent sensitivity (100%), specificity (94.3%), and predictive values. Elastase showed moderate-to-high diagnostic performance (AUC=0.811, threshold >49.2 µg/ml). Combined RSS>13 and salivary pH demonstrated robust diagnostic accuracy (SE=88.8%, SP=97.1%). Cholesterol positively correlated with 3-month RSS (r=0.538).

Conclusions: Salivary cholesterol, elastase, and the salivary pH emerge as promising diagnostic biomarkers for LPRD, demonstrating superior accuracy to other digestive enzymes and potential value in predicting treatment outcomes.