Parameters on esophageal pH-impedance monitoring that predict outcomes of patients with gastroesophageal reflux disease

Background & aims: pH-impedance monitoring detects acid and nonacid reflux events, but little is known about which parameters predict outcomes of different management strategies. We evaluated a cohort of medically and surgically managed patients after pH-impedance monitoring to identify factors that predict symptom improvement after therapy.

Methods: In a prospective study, we followed up 187 subjects undergoing pH-impedance testing from January 2005 through August 2010 at Washington University in St. Louis, Missouri (mean age, 53.8 ± 0.9 y; 70.6% female). Symptom questionnaires assessed dominant symptom intensity (DSI) and global symptom severity (GSS) at baseline and at follow-up evaluation. Data collected from pH impedance studies included acid exposure time (AET), reflux exposure time (RET) (duration of impedance decrease 5 cm above lower esophageal sphincter, reported as the percentage of time similar to AET), symptom reflux correlation (symptom index and symptom association probability [SAP]), and the total number of reflux events. Univariate and multivariate analyses were performed to determine factors associated with changes in DSI and GSS after therapy.

Results: Of the study subjects, 49.7% were tested on proton pump inhibitor (PPI) therapy and 68.4% were managed medically. After 39.9 ± 1.3 months of follow-up, DSI and GSS scores decreased significantly (P < .05). On univariate analysis, an abnormal AET predicted decreased DSI and GSS scores (P ≤ .049 for each comparison); RET and SAP from impedance-detected reflux events (P ≤ .03) also were predictive. On multivariate analysis, abnormal AET consistently predicted symptomatic outcome; other predictors included impedance-detected SAP, older age, and testing performed off PPI therapy. Abnormal RET, acid symptom index, or SAP, and numbers of reflux events did not independently predict a decrease in DSI or GSS scores.

Conclusions: Performing pH-impedance monitoring off PPI therapy best predicts response to antireflux therapy. Key parameters with predictive value include increased AET, and correlation between symptoms and reflux events detected by impedance.