Abstract
Mean nocturnal basal impedance (MNBI) measures an increase in mucosal permeability as a marker of mucosal damage from gastroesophageal reflux. It requires a transnasal catheter insertion for overnight monitoring which is inconvenient for many patients. More recently, one time measurement of mucosal impedance via balloon shows promise in the diagnosis of gastroesophageal reflux disease. We evaluated the diagnostic accuracy of short basal impedance in the reflux disease spectrum.
Consecutive adults undergoing impedance-pH monitoring off PPIs at our center between Oct. 2020 and Oct. 2022 were included. Studies were analyzed using Reflux Reader v 6.1 Medtronics, USA. Patients with achalasia or scleroderma were excluded. Pathological gastroesophageal reflux was defined as acid exposure time >4%, or DeMeester score of >14.7, or MNBI <2.23, or reflux episodes >80, or positive symptoms association determined by symptom association probability of >95%, or symptoms index of >50%. Short basal impedance was calculated from an average of 3 readings in the distal impedance measurement in a 10-minute window from the initial 30 minutes of catheter insertion from a 24-hour impedance-pH. Measurements were performed by one investigator blinded to other reflux parameters. Diagnostic performance was compared by calculating area under Receiver Operating Curve.
After excluding 2 patients with achalasia and 1 patient with scleroderma, a total of 100 patients were included in the study. Clinical characteristics are summarized in Table 1. Area under the curve for short basal impedance was 0.746, see Figure 1. The optimal cut off of short basal impedance was 1.96 kΩ. At this threshold, sensitivity was 64% and specificity was 81%.
Limitations: A small number of subjects, and lack of testing inter-observer agreement in the calculation of short basal impedance.
Short basal impedance shows good discrimination in pathological gastroesophageal reflux. If validated, short basal impedance has potential to replace 24-hour impedance pH-monitoring.