Comparison of Impedance and Pepsin Detection in the Laryngeal Mucosa to Determine Impedance Values that Indicate Pathological Laryngopharyngeal Reflux

OBJECTIVE: Recently, a 24-h impedance was used to detect laryngopharyngeal reflux (LPR). However, not every case of LPR is pathological. Thus, pathological pharyngeal impedance values need to be clearly established to diagnose pathological LPR. The aim of our study was to establish pathological 24-h pharyngoesophageal impedance/pH values for the diagnosis of LPR. METHODS: The study was conducted in a tertiary care setting. A total of 30 patients who were referred to microlaryngoscopy for a laryngeal pathology that might be caused by LPR were included in this prospective study. All patients were off proton-pump inhibitor therapy. The 24-h pharyngoesophageal impedance–pH monitoring was performed 1 day before surgery. A biopsy of laryngeal tissue was obtained during microlaryngoscopy and was analyzed by immunohistochemistry to detect pepsin. The patients were divided into two groups: pepsin negative and pepsin positive (which indicated pathological LPR). The results of 24-h multichannel intraluminal impedance–dual-channel pH monitoring were compared between the groups. The number of LPR episodes in the pepsin-positive group was analyzed to establish a cutoff value for pathological LPR. RESULTS: There were 18 participants in the pepsin-negative group and 12 in the pepsin-positive group. The median total pharyngeal refluxes detected were two (0–5) in the pepsin-negative group and 14 (6–39) in the pepsin-positive group (P<0.001), although the groups were otherwise homogeneous. There was a statistically significant difference in the number of all types of refluxes between groups. Six or more pharyngeal refluxes were the cutoff for the presence of pepsin in the laryngeal mucosa and, thereby, for the diagnosis of relevant/pathological LPR. CONCLUSION: Six or more pharyngeal reflux episodes registered during the 24-h impedance/pH monitoring seem to be the cutoff for diagnosing pathological LPR. Therefore, it is possible to suggest establishing this value as the pathological impedance value indicating pathological LPR. These results must be interpreted with caution due to the small sample size.