Reproducibility of 24-Hour Intraesophageal pH Monitoring

Abstract

To the Editor. I read with interest the article published in your journal by Mahajan et al1 concerning the reproducibility of 24-hour intraesophageal pH monitoring in children. I think that their article is an extremely important article with respect to understanding the limitations of ambulatory esophageal pH monitoring in children for the diagnosis of gastroesophageal reflux disease. The poor correlation that they found between the first and second 24-hour periods for patients studied with intraesophageal pH monitoring can be explained by additional factors that I do not believe they covered adequately in their article. These factors can be divided into technical problems and limitations with the equipment that they used and methodological problems with respect to the way in which they analyzed the esophageal pH record. The technical limitations and problems with respect to the equipment that they used involve the limitations of using a computerized system with a Digitrapper or storing data in a compartment where the data are later displayed on a computer screen and output using a printer. Unless the authors printed out each and every recording on a printer and went over the recordings, they cannot be sure that there were not equipment malfunctions that produced faults or misleading data that was interpreted as acid reflux. To the best of my knowledge, this equipment has an indicator for loose leads that will only detect loose leads in which there has been complete loss of electrical contact with the patient. Unfortunately, an incomplete loss of electrical contact with a loose lead, such as a loose reference electrode patch, cannot be detected by the machine and will produce a downward drift in the pH recording that would be misinterpreted by the computer, and possibly by the reader of the record, as acid reflux. This downward drift is …