Objective: To evaluate the diagnostic value and limitation of multichannel intraluminal esophageal impedance and pH (MII-pH) monitoring on the diagnosis of gastroesophageal reflux-related chronic cough (GERC).
Methods: The patients with suspicious GERC consecutively referred to our respiratory clinic between May 2010 and July 2011 underwent a MII-pH monitoring, and received anti-reflux drug therapy, irrespective of the laboratory findings. Chronic cough due to gastroesophageal reflux was determined when there was a favorable response to anti-reflux therapy. Then, the sensitivity, specificity, false positive and negative rate, total consistence, positively and negatively predictive value, the area under the curve of ROC and the Kappa value of the laboratory investigation were calculated for the diagnosis of GERC.
Results: During the research period, 56 patients completed MII-pH monitoring. Among them, the abnormal reflux was found in 35 patients, and GERC was finally confirmed in 30 patients (85.7%) including 25 patients (83.3%) due to acid reflux and 5 patients (16.7%) due to non-acid reflux. In the remaining 21 patients with normal reflux episodes, 6 patients (28.6%) could be explained by non-acid reflux for their cough because of a relatively predominant weakly acid reflux and favorable response to empirical anti-reflux therapy. For the diagnosis of GERC, MII-pH monitoring had the sensitivity of 83.3%, the specificity of 75.0%, false positive rate of 25.0%, false negative rate of 16.7%, total consistence of 80.4%, positive predictive value of 85.7%, negative predictive value of 71.4%, the area under the curve of ROC of 0.792 and Kappa value of 0.577 respectively.
Conclusion: MII-pH is a sensitive and reliable tool for the diagnosis of GERC due to its ability to detect both acid and non-acid reflux.