Acid-Based Parameters on pH-Impedance Testing Predict Symptom Improvement With Medical Management Better Than Impedance Parameters

OBJECTIVES: pH-impedance testing detects reflux events irrespective of pH, but its value in predicting treatment outcome is unclear. We prospectively evaluated subjects treated medically after pH-impedance testing to determine predictors of symptom improvement. METHODS: Subjects referred for pH-impedance testing completed questionnaires in which dominant symptoms and global symptom severity (GSS) were recorded. Acid-reflux parameters (acid-exposure time, AET; symptom association by Ghillebert probability estimate, GPE; symptom index, SI) and impedance reflux parameters (reflux-exposure time, RET; number of reflux events; GPE and SI with impedance data) were extracted. Symptoms and GSS were prospectively reevaluated after medical therapy. Univariate and multivariate analyses determined predictors of GSS improvement following medical management. RESULTS: Over 5 years, 128 subjects (mean 53.3±1.3 years, 66.4% female; typical symptoms 57.0%, 53.9% tested on therapy) underwent pH-impedance testing and subsequent medical therapy for reflux symptoms, and completed required questionnaires. On follow-up 3.35±0.14 years later, mean GSS declined by 45.0%, with 42.2% patients reporting ≥50% GSS improvement. On univariate analysis, total AET, AET≥4.0%, and GPE for all reflux events predicted both linear and ≥50% GSS improvement, but RET and number of reflux events did not. On multivariate analysis, controlling for testing on or off therapy, only AET (P=0.003) and GPE for all reflux events (P=0.029) predicted GSS improvement. CONCLUSIONS: Acid-based reflux parameters offer greater value over impedance-based nonacid-reflux parameters in predicting symptomatic responses to proton pump inhibitor (PPI) therapy. Our findings support conducting pH-impedance studies off PPI therapy to maximize clinical utility in predicting outcome.