The Role of Proximal pH Monitoring

Abstract

TO THE EDITOR: In the December issue of the Journal, Cool et al. (1) present a carefully designed study evaluating the role of proximal pH monitoring in diagnosing patients with typical and atypical GERD symptoms. Finding that proximal pH monitoring changed the study interpretation in only 20 (6%) of their 346 patients, the authors argued against using this technique for routine clinical use. While we agree with the finding that proximal pH monitoring identifies abnormal amounts of reflux in a small proportion of patients with normal distal esophageal acid exposure, there is another perspective that should be addressed. We find the addition of proximal pH electrode useful during routine pH monitoring in our clinical practice. In our experience, recording proximal pH is important in differentiating distal esophageal drops in pH due to actual gastroesophageal reflux from artifactual pH drops caused by the ingestion of acidic foods or beverages not recorded by patients (Fig. 1). Studies from our laboratory in healthy volunteers identified that many commonly ingested foods produce distal esophageal pH values below during ingestion (2). Reviewing patient diaries obtained during pH monitoring we found that more than three-quarters of our patients ingested at least one of these foods during pH testing with carbonated beverages being most frequent. In addition, by using dual pH technique we could exclude artifactual reflux caused by acidic drinks not recorded in the diary.