From the AGA Journals

Acid exposure time found most useful in pH-impedance testing



pH-impedance testing best predicted response to reflux treatment when patients were off proton pump inhibitors, and abnormal acid exposure time was the single most useful testing parameter, a prospective study has found.

“Impedance-based reflux parameters complement but do not replace acid-based parameters in predicting symptom outcome from both medical and surgical antireflux therapy,” wrote Dr. Amit Patel and his associates at the Washington School of Medicine, St. Louis. The study appears in the May issue of Clinical Gastroenterology and Hepatology (doi:10.1016/j.cgh.2014.08.02).

“Because abnormal acid reflux time and symptom-reflux correlation parameters are detected more often when testing is performed off therapy, pH-impedance testing off antisecretory therapy maximizes prediction of symptomatic outcome from GERD [gastroesophageal reflux disease] therapy,” the researchers wrote.

Clinicians continue to debate the role of pH-impedance testing in management of GERD, whether testing should be performed on or off antisecretory therapy, and which testing parameters are most useful for predicting treatment response, the investigators noted. Therefore, they followed 187 adults with persistent GERD symptoms who underwent pH-impedance testing at their center during a 5-year period. Average age of patients was 54 years, almost 71% were female, and none had histopathologic evidence of esophageal motor disorders. Almost half had been off proton pump inhibitors for 7 days when tested, and 68% were managed medically as opposed to surgically.

Global symptom assessment (GSS) and dominant symptom intensity (DSI) scores both improved significantly during an average of 40 months of follow-up, the researchers said. After the researchers controlled for demographics, symptoms at presentation, use of proton pump inhibitors (PPI), and parameters that predicted treatment response in the univariate analyses, only abnormal acid exposure time (AET) predicted linear improvement in DSI scores (P =.027), while abnormal AET (P =.002) and symptom association probability (P =.026) predicted significant improvements in linear and dichotomous GSS, they reported. Abnormal AET and being off PPIs during testing also more than doubled the odds of at least a 50% improvement in GSS.

In contrast, dichotomous reflux exposure time did not predict response in any of the analyses, said the investigators. “Established thresholds for the total number of reflux events did not predict linear or dichotomous global symptom severity improvement,” they added. “Our data therefore suggest that performing pH-impedance testing off PPI therapy increases the yield of abnormal AET and symptom-reflux association with reflux events, facilitating predicting value for symptom improvement with both medical and surgical antireflux therapy.”

The researchers could not corroborate patients’ compliance with antisecretory therapy, assess the reasons physicians chose medical or surgical management, or evaluate the impact of the placebo effect or other factors unrelated to reflux, they said.

The study was partly funded by the National Institute for Diabetes and Digestive and Kidney Diseases, the National Institutes of Health, and the Washington University Department of Medicine Mentors in Medicine and Clinical Science Training and Research programs. The authors declared no relevant conflicts of interest.

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