[The diagnostic value of symptom index in gastroesophageal reflux-induced chronic cough].
OBJECTIVE
To explore the diagnostic value and optimal cut-off point of symptom index (SI) in gastroesophageal reflux-induced chronic cough (GERC).


METHODS
The recordings of multichannel intraluminal esophageal impedance and pH monitoring were retrospectively analyzed in 118 patients with suspicious GERC. SI for all the refluxes, acid reflux and non-acid reflux was calculated respectively by analyzing the temporal association between detected reflux and cough recorded on diary card. Based on the favorable response to the anti-reflux therapy, the diagnostic value for GERC of SI was evaluated and compared with that of the symptom association probability (SAP).


RESULTS
GERC was definitely determined in 100 patients (84.7%). When SI for all the refluxes was used for the diagnosis of GERC, the cut-off point of ≥ 45% had the highest diagnostic efficacy, with the sensitivity of 56.0%, the specificity of 83.3% and Youden index of 0.393. SI for acid or non-acid reflux had the same optimal cut-off point of ≥ 30% and presented with the similar efficacy in the diagnosis of acid or non-acid GERC. Compared with SAP of ≥ 75%, SI for all the refluxes of ≥ 45% had a lower sensitivity (56.0% vs 75.0%, χ(2) = 7.988, P = 0.005), a higher specificity (83.3% vs 44.4%, χ(2) = 5.900, P = 0.015) and the comparable positive or negative predictive value in the diagnosis of GERC. The diagnostic accuracy for GERC was further improved when combining SI for all the refluxes with SAP.


CONCLUSIONS
SI for all the refluxes has a diagnostic value similar to SAP and its optimal cut-off point for GERC may be ≥ 45%.
Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China.
Zhongmin
Z
Yang
Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China.
Xianghuai
X
Xu
Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China.
Qiang
Q
Chen
Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China.
Li
L
Yu
Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China.
Siwei
S
Liang
Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China.
Hanjing
H
Lyu
Department of Respiratory Medicine, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China. Email: qiuzhongmin@tongji.edu.cn.
Zhongmin
Z
Qiu
D000328:Adult; D003371:Cough / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D005764:Gastroesophageal Reflux / Q000150:complications / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D063189:Symptom Assessment