The utility of oesophageal pH monitoring in diagnosing gastroesophageal reflux disease-related chronic cough.

BACKGROUND

Chronic cough is a common medical complaint, which may deteriorate patients' quality of life and cause many complications. Gastroesophageal reflux disease (GERD) is one of the frequent reasons for chronic cough. Oesophageal pH monitoring is one of the diagnostic methods performed to confirm diagnosis of GERD-related cough. The aim of the study was to analyse the utility of oesophageal pH monitoring in diagnosing GERD-related cough and to identify the most sensitive pH monitoring parameters for diagnosing GERD-related cough.

METHODS

24-hour oesophageal pH monitoring was performed in 204 patients suffering from chronic cough. The group consisted of 65% females and the median age was 59 years. An acid reflux episode was defined as a rapid drop in pH to a value below 4 for at least 12 seconds. The diagnosis of GERD was based on total fraction time of pH < 4, upright or supine fraction time of pH < 4, or DeMeester score. The diagnosis of GERD-related cough was made if cough episodes, marked by the patients, appeared within 2 minutes after the reflux. The association between reflux episode and appearance of cough was analysed using two parameters: symptom index (SI ≥ 50%) and/or symptom association probability (SAP ≥ 95%).

RESULTS

Based on results of pH monitoring, 135 patients (135/204, 66%) were diagnosed with GERD. Among them, 117 patients (117/135, 87%) were diagnosed based on DeMeester score. Among patients with GERD, 61 patients met the criteria of GERD-related cough (61/135, 45%), i.e. 30% of the group as a whole. Thirty-six patients (36/61, 59%) were diagnosed based on SAP, 12 patients (20%) based on SI, and 13 (21%) based on both parameters. Spearman rank correlation coefficient for SAP ≥ 95% and SI ≥ 50% was 0.46 (p < 0.05).

CONCLUSIONS

Based on pH monitoring results, GERD was diagnosed twice as often as GERD-related cough. SAP index is more sensitive than SI for the diagnosis of GERD-related cough.