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Clin Gastroenterol Hepatol. 2015 May;13(5):884-91. doi: 10.1016/j.cgh.2014.08.029. Epub 2014 Aug 23.

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

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Division of Gastroenterology, Washington University School of Medicine, Saint Louis, Missouri.
Division of Gastroenterology, Washington University School of Medicine, Saint Louis, Missouri. Electronic address:



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.


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.


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.


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.


Esophageal pH-Impedance Monitoring; GERD; PPI; Response to Therapy; Symptom-Reflux Correlation

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