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Original Research: Signs and Symptoms of Chest Disease |

Comparison of Gastroesophageal Reflux Disease Questionnaire and Multichannel Intraluminal Impedance pH Monitoring in Identifying Patients With Chronic Cough Responsive to Antireflux TherapyPrediction of Cough Due to Reflux FREE TO VIEW

Xianghuai Xu, MD; Qiang Chen, MD; Siwei Liang, MD; Hanjing Lv, MD; Zhongmin Qiu, MD, FCCP
Author and Funding Information

From the Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai, China.

Correspondence to: Zhongmin Qiu, MD, FCCP, Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Rd, Shanghai 200065, China; e-mail: qiuzhongmin@tongji.edu.cn


Part of this article was presented orally at the Seventh International Cough Symposium 2012: Taming of Chronic Cough, July 5-7, 2012, London, England.

Funding/Support: This study was supported by grants from the National Natural Science Foundation of China [81170079] and Shanghai Shenkang Hospital Development Center [SHDC12012211].

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;145(6):1264-1270. doi:10.1378/chest.13-1634
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Background:  Empirical therapy has been recommended as an initial clinical approach for treating gastroesophageal reflux-induced chronic cough (GERC). This study compared the predictive accuracy of the Gastroesophageal Reflux Disease Questionnaire (GerdQ) with the accuracy of multichannel intraluminal impedance pH monitoring (MII-pH) for GERC.

Methods:  A total of 126 consecutive patients with potential GERC were recruited to undergo MII-pH and complete the GerdQ. A final diagnosis of GERC was made after favorable response to consequent medicinal antireflux therapy, regardless of laboratory findings. The predictive accuracy of the GerdQ for GERC was assessed and compared with that of MII-pH.

Results:  GERC was confirmed in 102 of 126 patients (81.0%); cough was due to acid reflux in 55 (53.9%) and nonacid reflux in 47 (46.1%). The optimal cutoff point of the GerdQ for predicting GERC was defined as 8.0 according to the highest Youden index of 0.584, with a sensitivity of 66.7%, specificity of 91.7%, positive predictive value of 97.1%, and negative predictive value of 42.9%. A subanalysis for only acid GERC showed further improvement in the predictive accuracy of the GerdQ, corresponding to a sensitivity of 90.9%, specificity of 78.6%, positive predictive value of 71.4%, and negative predictive value of 96.4%. However, a meaningful GerdQ cutoff point for prediction of nonacid GERC could not be determined. In general, MII-pH was superior to the GerdQ for predicting GERC and acid GERC.

Conclusions:  The GerdQ can be used for predicting acid GERC but not nonacid GERC and is inferior to MII-pH.

Trial registry:  Chinese Clinical Trial Registry; No.: ChiCTR-ODT-12001899; URL: www.chictr.org

Figures in this Article

Gastroesophageal reflux is a common cause of chronic cough.1,2 Based on pH values of refluxate in the esophagus, gastroesophageal reflux-induced chronic cough (GERC) can be classified as acid or nonacid.3

Multichannel intraluminal impedance pH monitoring (MII-pH) can detect both acid and nonacid reflux4 and is the most sensitive and specific test for diagnosing GERC. Unfortunately, MII-pH has not been extensively used clinically because of its invasiveness and limited availability. Alternatively, empirical therapy has been advocated as an initial approach for treating GERC.1,5,6 Because empirical trials frequently fail to relieve patients’ cough,7 screening patients with potential GERC prior to antireflux treatment may improve therapeutic gains.

The Gastroesophageal Reflux Disease Questionnaire (GerdQ) is a patient-centered and self-reported diagnostic instrument for gastroesophageal reflux disease (GERD)8 and can achieve an overall diagnostic accuracy similar to that made by a gastroenterologist, with a sensitivity of 64.6% and a specificity of 71.4%.8,9 However, to our knowledge the usefulness of the GerdQ in GERC diagnosis has never been addressed. Therefore, we conducted a prospective study to compare the predictive accuracies of the GerdQ and MII-pH for GERC.

Patients

Consecutive patients referred to our respiratory clinic for potential GERC between January 2011 and March 2013 were recruited for this study. Requirements for participation included any one of the following: (1) presence of chronic cough and typical reflux-related symptoms, (2) GERC considered when previous laboratory workups failed to identify other possible causes of chronic cough,10 and (3) coexisting GERC suspected when the treatment of current etiologies failed to completely resolve a cough. Patients refusing to undergo or who were intolerant of MII-pH were excluded. The study protocol was approved by the ethics committee of Tongji Hospital [No. LL(H)-11-13] and registered with the Chinese Clinical Trials Register. Written informed consent was obtained from all subjects before enrollment.

Study Design

This was a single-center observational study. Initial patient assessments included a medical history, physical examination, plain chest radiography, lung function tests, and evaluation of cough severity as determined by validated cough symptom scores that rate a cough using six incremental scales (0 = no cough, 5 = worst cough)11 (e-Appendix 1). Additionally, patients were evaluated with the previously validated Chinese version of the GerdQ12,13 (e-Appendix 2).

The GerdQ comprises six symptom-related items consisting of four reflux-related items positively related to GERD and two items negatively related to GERD. Patients were asked to recall how often they experienced the events described in the questionnaire during the preceding week and to score their answers on a four-point scale ranging from 0 to 3 for positive predictors and from 3 to 0 for negative predictors. The total scores represented a GerdQ score ranging from 0 to 18. A higher score signifies a greater possibility of GERD.8

MII-pH was performed as previously described3 after the patients had stopped taking acid-suppressing medication for at least 1 week. Briefly, a combined MII-pH catheter was inserted transnasally into the patient’s esophagus, with six impedance channel sensors (K6011-E10632; Unisensor AG) located 3, 5, 7, 9, 15, and 17 cm above the lower esophageal sphincter and an antimony pH electrode (819100; Medical Measurement System BV) positioned 5 cm above the proximal border of the lower esophageal sphincter. A connected portable data logger (Ohmega; Medical Measurement System BV) stored data from all seven channels over 24 h. Reflux episodes recorded on the tracings of MII-pH were manually characterized by their impedance value as liquid, gas, or mixed liquid-gas reflux or characterized using a pH meter as acidic (pH < 4.0), weakly acidic (pH 4.0-7.0), or weakly alkaline (pH > 7.0) reflux, with the latter two collectively referred to as nonacid reflux. The DeMeester score was calculated as a global measure of esophageal acid exposure. Symptom association probability (SAP) was used to represent the temporal association between cough recorded by patients on diary cards and reflux that had occurred during the preceding 2-min period.3,14 Abnormal acid reflux was defined as a DeMeester score ≥ 14.72, SAP for acid reflux ≥ 95%, or both. These scores were used for diagnosing acid GERC, whereas abnormal nonacid reflux was defined as an SAP for nonacid reflux ≥ 95%, which was used for diagnosing nonacid GERC.3

Regardless of MII-pH findings, all patients received an 8-week course of standard antireflux therapy consisting of omeprazole 20 mg bid and domperidone 10 mg tid. If the initial treatment failed and MII-pH revealed abnormal reflux, patients received an augmented antireflux trial by doubling the dose of omeprazole to 80 mg/d or replacing domperidone with baclofen 20 mg tid.15 All study patients and investigators were blinded to GerdQ scores throughout treatment. GERC was finally diagnosed only when a cough disappeared (resolved completely) or improved (combined daytime and nighttime cough symptom score decreased by ≥ 2 points)3 as recommended by American College of Chest Physicians guidelines.1 The predictive accuracies of the GerdQ and MII-pH for GERC were analyzed and compared (Fig 1).

Figure Jump LinkFigure 1. CONSORT (Consolidated Standards of Reporting Trials) flow diagram of the study and algorithm for GERC. GERC = gastroesophageal reflux-induced chronic cough; GerdQ = Gastroesophageal Reflux Disease Questionnaire; MII-pH = multichannel intraluminal impedance pH monitoring.Grahic Jump Location
Statistical Analysis

Data with normal distributions are expressed as mean ± SD, whereas data with skewed distributions are expressed as median values (interquartile range). Unpaired Student t and Mann-Whitney U tests were used for data comparison where applicable. Receiver operating characteristic analysis was used to evaluate the predictive value of the GerdQ. The optimal cutoff point was determined on the basis of the highest Youden index. The relation between the GerdQ score and DeMeester score or SAP for acid reflux was analyzed by linear regression. Predictive values of the GerdQ and MII-pH were compared with the χ2 test. Diagnostic consistency was evaluated by κ test. Statistical calculations were performed with SPSS, version 17.0 (IBM) software.

Demographic Characteristics

A total of 167 of 583 patients with chronic cough (28.6%) met the inclusion criteria for this study. Among this group of eligible patients, 126 (76%) completed evaluations by MII-pH and the GerdQ. Demographic characteristics of the final study group are shown in Table 1.

Table Graphic Jump Location
Table 1 —Patient Demographic Characteristics

Data are presented as mean ± SD, median (interquartile range), or No. (%) unless otherwise indicated.

Abnormal reflux was revealed by MII-pH in 108 of 126 patients (85.7%), and GERC was confirmed by empirical antireflux treatment in 80 patients (74.1%). Twenty-eight patients (25.9%) received augmented acid suppression treatment with omeprazole 80 mg/d, and GERC was confirmed in 11 patients (39.3%). The remaining 17 patients (15.7%) accepted therapy with baclofen, and GERC was further confirmed in eight (47.1%). Among nine nonresponders, cough in seven (77.8%) could be explained by upper-airway cough syndrome in two (22.2%) and cough variant asthma in five (55.6%), but the causes were unknown in two (22.2%). In 18 patients (14.3%) with a negative DeMeester score and SAP, nonacid GERC was determined in three patients (16.7%) on the basis of increased weakly acidic reflux events and favorable response to antireflux treatment. In total, GERC was diagnosed in 102 patients (81.0%), including 55 with acid GERC (53.9%) and 47 with nonacid GERC (46.1%). Additionally, the cough was completely resolved in 38 patients (69.1%) with acid GERC and 25 (53.2%) with nonacid GERC. A plot of patient response vs treatment time is shown in Figure 2.

Figure Jump LinkFigure 2. A-C, Changes in cough symptom score over time in the patients with definite GERC responsive to antireflux therapy. A, GERC. B, Acid GERC. C, Nonacide GERC. See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
The GerdQ in Predicting GERC

On the basis of the highest Youden index of 0.584, the optimal cutoff point of the GerdQ for predicting GERC was defined at 8.0. The sensitivity, specificity, positive and negative predictive values, and area under the curve for this score are shown in Table 2 and Figure 3A. GERC was confirmed in 68 of 70 patients with a positive GerdQ score (97.1%), including 50 with acid GERC (73.5%) and 18 with nonacid GERC (26.5%). Additionally, GERC was verified in 34 of 56 patients with a negative GerdQ score (60.7%), including five with acid GERC (14.7%) and 29 with nonacid GERC (85.3%). Patients with acid GERC had a higher GerdQ score than those with nonacid GERC (10.63 ± 2.06 vs 7.38 ± 1.39, respectively; t = 6.700; P = .000). Moreover, patients with GERC and a positive GerdQ score presented with more frequent heartburn, regurgitation, and use of additional medication (Table 3).

Table Graphic Jump Location
Table 2 —Prediction of GERC Between GerdQ Score ≥ 8 and MII-pH

GERC = gastroesophageal reflux-induced chronic cough; GerdQ = Gastroesophageal Reflux Disease Questionnaire; MII-pH = multichannel intraluminal impedance pH monitoring.

Figure Jump LinkFigure 3. A, B, Receiver operating curve of the GerdQ for predicting GERC. AUC, sensitivity, and 1-specificity by cutoff point of GerdQ score for GERC (A) and acid GERC (B). AUC = area under the curve. See Figure 1 legend for expansion of other abbreviations.Grahic Jump Location
Table Graphic Jump Location
Table 3 —Distribution of Items in Patients With GERC With Positive and Negative GerdQ Scores

Data are presented as mean ± SD unless otherwise indicated. See Table 2 legend for expansion of abbreviations.

A subanalysis for predicting acid GERC showed the same optimal cutoff point of 8.0; its sensitivity, negative predictive value, and the area under the curve increased, whereas its specificity and positive predictive value decreased (Fig 3B, Table 4). Fifty of 55 patients with acid GERC (90.9%) had a positive GerdQ score. There was a significant positive linear correlation between the GerdQ and DeMeester scores (r = 0.793, P = .000) (Fig 4) but not between the GerdQ score and SAP for acid reflux (r = 0.159, P = .296). When predicting nonacid GERC alone, the area under the curve of the GerdQ was 0.310, and no objective meaningful cutoff point could be determined.

Table Graphic Jump Location
Table 4 —Prediction of Acid GERC Between GerdQ Score ≥ 8 and MII-pH

See Table 2 legend for expansion of abbreviations.

Figure Jump LinkFigure 4. Relationship between GerdQ score and DeMeester score in patients with acid GERC analyzed by linear regression (r = 0.793, P = .000). See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
Comparison of The GerdQ and MII-pH in Predicting GERC

The GerdQ had a lower sensitivity, negative predictive value, and κ value than MII-pH but showed higher specificity and a comparable positive predictive value (Table 2). When used only for predicting acid GERC, the GerdQ still had a lower sensitivity, specificity, positive predictive value, Youden index, and κ value, but its negative predictive value was similar to that of MII-pH (Table 4).

For prediction of GERC, there was a 60.8% overlap between the GerdQ and MII-pH. Additionally, 30.4% and 5.9% of GERC cases were exclusively predicted by MII-pH and GerdQ, respectively. MII-pH and GerdQ failed to predict only 2.9% of GERC cases (Fig 5).

Figure Jump LinkFigure 5. Predicted proportion of GERC by GerdQ and MII-pH. See Figure 1 legend for expansion of abbreviations.Grahic Jump Location

Cough is not a typical symptom of GERD and can be caused by many other diseases. Generally, patients with obvious regurgitation and heartburn have a higher likelihood that their cough is due to reflux.16 Thus, GERC may be predicted by the GerdQ because it primarily and quantitatively evaluates the frequency and intensity of these symptoms.8 The optimal cutoff GerdQ score (8.0) for predicting GERC was consistent with that previously reported in patients with GERD,8 corresponding to a sensitivity of 66.7% and a specificity of 91.7%. When used only for acid GERC, the GerdQ demonstrated higher sensitivity but at the cost of lower specificity. Therefore, GerdQ can be used for screening acid GERC and selecting the appropriate patients for the appropriate treatment and can reduce the need for MII-pH and conserve medical resources.

Proton pump inhibitors alone or in combination with prokinetic agents are considered to be the cornerstone of antireflux pharmacotherapy.1,5,6 However, there is controversy regarding their therapeutic efficacy for GERC.1719 A recent systematic review favored using proton pump inhibitors for treating GERC if patients have pathogenic esophageal acid exposure.20 This recommendation is supported by the present data, showing that standard or augmented acid suppression therapy containing omeprazole resolved cough in most patients with GERC, with a slight delay of cough resolution in nonacid GERC compared with acid GERC (9.91 ± 1.59 weeks vs 8.36 ± 0.75 weeks, respectively; t = 6.455; P = .000). The patients may represent a more rigorously selected population with a higher likelihood of GERC as demonstrated by MII-pH. The difference in patient recruitment may help to explain the high success rate of antireflux therapy.

Microaspiration and esophageal-tracheobronchial reflex are the main mechanisms underlying GERC.1,5 Proton pump inhibitors can reduce the acidity and volume of refluxate and even decrease reflux episodes when combined with prokinetic agents.21 Even for cough caused by weakly acidic reflux, which accounts for the majority of nonacid reflux,22 a mild increase in the pH value of refluxate might result in a significant blockade of acid signal transduction in a hypersensitive esophagus followed by cough resolution.23 However, proton pump inhibitors cannot modify transient lower esophageal sphincter relaxations, which are more frequently involved in GERC.24 Baclofen, a potent agonist of γ-aminobutyric acid B receptor, may help to control cough because it inhibits both acid and nonacid reflux through rectifying transient lower esophageal sphincter relaxations.15,25 In addition, baclofen has a nonspecific antitussive activity and is used to treat refractory cough caused by diverse etiologies.26 In the present study, cough in 8.0% of patients with GERC resistant to acid suppression was resolved with baclofen as an add-on therapy. Although we cannot separate its antireflux effect from its nonspecific antitussive activity in the study, baclofen can become a treatment option for GERC refractory to proton pump inhibitors.

Reflux-related symptoms may be associated with the type of reflux involved. Most regurgitation and heartburn are caused by acid reflux,27 and nonacid reflux is responsible for only a minority of these symptoms in patients.28,29 This fact is further reinforced by the present findings that patients with GERC with positive GerdQ scores presented with more frequent heartburn and regurgitation, and GerdQ scores were significantly related to DeMeester scores in patients with acid GERC. This finding may explain why the GerdQ was a more accurate predictor for acid GERC.

The GerdQ demonstrated a suboptimal sensitivity and specificity in predicting GERC, possibly reflecting the inherent imbalance between cough and the other reflux symptoms in GERC. Cough is usually the sole or predominant complaint of patients with GERC, and the other reflux-related symptoms may be rare or absent.30 When patients lack or have no obvious regurgitation and heartburn, GerdQ cannot predict GERC. The GerdQ correctly identified only 66.7% of GERC cases, which is consistent with two studies of the GerdQ in patients with GERD.14,31 Therefore, the GerdQ is imperfect for predicting GERC because a negative GerdQ score cannot exclude the possibility of GERC.

MII-pH provides information about the temporal association between cough and acid or nonacid reflux.32 Not surprisingly, MII-pH is superior to the GerdQ for predicting both acid and nonacid GERC and cannot be completely replaced by the GerdQ. Nevertheless, MII-pH is far from perfect because it depends on SAP in the diagnosis of GERC, and SAP is not adequately reliable because patients usually underestimate the frequency or misreport the timing of cough events.33,34 Considering its invasive and expensive nature, MII-pH is currently less cost-effective than the GerdQ in the diagnosis of GERC.

There are several limitations of this study. GERC was defined by favorable responsiveness to medicinal therapy, which might have led to an underdiagnosis of some GERC cases resistant to medicinal treatments but responsive to other therapies, such as antireflux surgery. The strict inclusion criteria possibly resulted in selection bias; therefore, the characteristics of the enrollees may not resemble those of a typical population with cough visiting a physician. Nevertheless, these patients are usually potential candidates for empirical antireflux therapy and need to be screened with the GerdQ before therapy. The GerdQ is initially designed for GERD and lacks the items related to cough. However, addition of cough evaluation items to the GerdQ would not likely improve its predictive accuracy because the characteristics and timing of a cough do not provide clues about the cause of cough.35 Furthermore, the GerdQ is useless for nonacid GERC. However, even though it is imperfect, use of the GerdQ should be considered first to avoid overuse of empirical antireflux therapy. If a patient with a positive GerdQ score does not respond to consequent empirical antireflux therapy or presents with a negative GerdQ score, MII-pH must be performed to identify reflux as a cause of chronic cough. In conclusion, the GerdQ can be used for predicting acid GERC but not nonacid GERC. GerdQ is inferior to MII-pH.

Author contributions: Dr Xu had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Dr Xu: contributed to the case collection and processing, statistical analysis of data, interpretation of results, and writing of the manuscript.

Dr Chen: contributed to the case collection and critical review of the manuscript.

Dr Liang: contributed to the case collection and critical review of the manuscript.

Dr Lv: contributed to the case collection and critical review of the manuscript.

Dr Qiu: contributed to the study design, program coordination, and review and correction of the manuscript.

Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Role of sponsors: The sponsors had no role in the study design, cases collection, data analysis and manuscript submission. The opinions expressed in this paper reflect those of the authors and do not represent those of The National Natural Science Foundation of China and Shanghai Shenkang Hospital Development Center.

Other contributions: The authors thank AstraZeneca AB (Sweden) for permission to use a Chinese version of the GerdQ in this study.

Additional information: The e-Appendixes can be found in the “Supplemental Materials” area of the online article.

GERC

gastroesophageal reflux-induced chronic cough

GERD

gastroesophageal reflux disease

GerdQ

Gastroesophageal Reflux Disease Questionnaire

MII-pH

multichannel intraluminal impedance pH monitoring

SAP

symptom association probability

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Figures

Figure Jump LinkFigure 1. CONSORT (Consolidated Standards of Reporting Trials) flow diagram of the study and algorithm for GERC. GERC = gastroesophageal reflux-induced chronic cough; GerdQ = Gastroesophageal Reflux Disease Questionnaire; MII-pH = multichannel intraluminal impedance pH monitoring.Grahic Jump Location
Figure Jump LinkFigure 2. A-C, Changes in cough symptom score over time in the patients with definite GERC responsive to antireflux therapy. A, GERC. B, Acid GERC. C, Nonacide GERC. See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
Figure Jump LinkFigure 3. A, B, Receiver operating curve of the GerdQ for predicting GERC. AUC, sensitivity, and 1-specificity by cutoff point of GerdQ score for GERC (A) and acid GERC (B). AUC = area under the curve. See Figure 1 legend for expansion of other abbreviations.Grahic Jump Location
Figure Jump LinkFigure 4. Relationship between GerdQ score and DeMeester score in patients with acid GERC analyzed by linear regression (r = 0.793, P = .000). See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
Figure Jump LinkFigure 5. Predicted proportion of GERC by GerdQ and MII-pH. See Figure 1 legend for expansion of abbreviations.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1 —Patient Demographic Characteristics

Data are presented as mean ± SD, median (interquartile range), or No. (%) unless otherwise indicated.

Table Graphic Jump Location
Table 2 —Prediction of GERC Between GerdQ Score ≥ 8 and MII-pH

GERC = gastroesophageal reflux-induced chronic cough; GerdQ = Gastroesophageal Reflux Disease Questionnaire; MII-pH = multichannel intraluminal impedance pH monitoring.

Table Graphic Jump Location
Table 3 —Distribution of Items in Patients With GERC With Positive and Negative GerdQ Scores

Data are presented as mean ± SD unless otherwise indicated. See Table 2 legend for expansion of abbreviations.

Table Graphic Jump Location
Table 4 —Prediction of Acid GERC Between GerdQ Score ≥ 8 and MII-pH

See Table 2 legend for expansion of abbreviations.

References

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