Acid Perfusion Test: A Useful Test for Evaluating Esophageal Acid Sensitivity?

Abstract

To the Editor: In a recent issue of Digestive Disease and Sciences, King et al. reported the results of a comparison of the esophageal acid perfusion test (APT) and ambulatory pH monitoring with symptom association analysis in patients with suspected gastroesophageal reflux disease [1]. Patients with a positive APT were found to have a significantly higher symptom index (SI), symptom sensitivity index (SSI), and symptom association probability (SAP) compared to patients with a negative APT. In previous studies comparing the outcome of APT and 24-hr pH monitoring, the association between these tests was found to be weak [2–5]. It was felt that the “endogenous Bernstein test” constituted by pH monitoring was at least as good as and more physiological than the APT, and the APT disappeared from the armamentarium of most gastroenterology services in the early nineties. In their paper, King et al. state that the APT is useful for the evaluation of esophageal acid sensitivity, in particular, in patients in whom a symptom-reflux association cannot be demonstrated by 24-hr pH-metry. In the words of the authors, “It is possible that the APT may detect acid sensitivity in some patients with false-negative 24-hr pH studies.” We agree that this is possible, but it is also possible that the APT yields false-positive results in some patients with truly negative 24-hr pH studies. Since the study by King et al. did not include healthy subjects, we do not know how many of these would have had a positive APT. Forty-eight of the 162 patients with a negative SI (29.6%) had a positive APT, and of the subgroup of 86 patients who