Long-term therapeutic outcome of patients undergoing ambulatory pH monitoring for chronic unexplained cough

Abstract

Background and aim: Ambulatory pH monitoring is frequently performed to determine temporal associations between reflux events and chronic unexplained cough. We further explored the clinical value of ambulatory pH monitoring in predicting long-term symptomatic outcome of therapy in chronic cough.

Methods: Symptom scores and reflux indicators from ambulatory pH study [acid exposure time, symptom association probability (SAP), and symptom index] were extracted from records of subjects undergoing esophageal evaluation for chronic cough. Intensity of antireflux therapy administered and symptomatic outcome were determined by telephone interview. Univariate and logistic regression analysis were performed to identify predictors of a high degree response (HDR), defined as sustained, durable symptom improvement lasting >3 months.

Results: Fifty-three subjects (mean age 63+/-2 y, 42 females) fulfilled the inclusion criteria. Reflux parameters were abnormal on ambulatory pH monitoring in 54.7%. After a mean interval of 3+/-0.3 years, cough intensity improved significantly, 19 subjects (35.8%) achieving HDR. Only female sex and positive SAP predicted HDR on univariate analysis; SAP and intensity of antireflux therapy were retained as independent predictors (P<or=0.03) on logistic regression analysis. Sequential use of acid exposure time, SAP, and symptom index had the best value, with the highest likelihood of HDR when all three were positive (85.7%, P<0.01).

Conclusions: Reflux disease is a frequent cause of chronic unexplained cough and aggressive antireflux therapy forms a vital component of management. Positive SAP is an independent predictor of outcome, but hierarchical or sequential use of abnormal gastroesophageal reflux disease parameters on ambulatory pH testing has value in predicting long-term symptomatic response.

FIGURE 1

Hierarchical use of parameters from ambulatory pH testing in predicting response to antireflux therapy. The highest likelihood of a sustained, durable response (high degree response, HDR) to antireflux therapy was achieved when acid exposure time (AET), symptom association probability (SAP) and symptom index (SI) were all abnormal (P < 0.01).

FIGURE 2

Relationship between intensity of GERD therapy, GERD evidence on pH study and high degree response (HDR). Evidence of GERD on pH study prompted more aggressive therapy recommendations by treating physicians (P < 0.05 across groups), which in turn resulted in a higher frequency of high degree response (P = 0.02 across groups). GERD indicates gastroesophageal reflux disease.

FIGURE 3

Results of logistic regression analysis using high degree response (HDR) as the outcome variable. Female sex, positive SAP (but not elevated AET, abnormal SI, or esophageal motor pattern) and intensity of GERD therapy predicted HDR. AET indicates acid exposure time; GERD, gastroesophageal reflux disease; SAP, symptom association probability; SI, symptom index.