Diagnostic yield of oesophageal pH monitoring in patients with chronic unexplained cough

Objective. One of the main causes of persistent cough is gastro-oesophageal reflux. In these patients, excessive oesophageal acid exposure and/or a temporal association between gastro-oesophageal reflux and cough can be demonstrated during 24-h pH monitoring. Impedance pH monitoring may have a higher yield than pH monitoring alone, but this technique is not yet widely available. The aim of this study was to assess the diagnostic yield of ambulatory 24-h oesophageal pH monitoring for the evaluation of chronic unexplained cough. Material and methods. Twenty-four-hour pH monitoring studies were analysed in 55 patients with chronic cough. In 14 of these studies concurrent ambulatory pressure monitoring was done. A cough episode was considered to be related to reflux if the cough occurred within two minutes after the onset of the reflux episode (reflux-cough sequence''). Temporal relationships between cough and reflux were expressed by using the symptom association probability (SAP). Results. Thirty-seven patients actually coughed during the 24-h study. Eleven patients (20%) had a positive SAP for the reflux-cough sequence. In 5 patients, reflux followed coughing. Pathological oesophageal acid exposure was found in 15 subjects. Interestingly, only a minority (39.2%) of the cough bursts detected manometrically were marked by patients who had undergone both combined 24-h pH and pressure recording. Conclusions. This study shows that, in a routine clinical setting, combined 24-h pH and pressure monitoring is useful in the evaluation of patients with chronic unexplained cough, as positive findings are not infrequently found and have diagnostic and therapeutic consequences.