The clinical utility of flexible bronchoscopy in the evaluation of chronic cough

Flexible bronchoscopy in the diagnosis of chronic cough causes in non-smoking adults

A chronic cough (CC) is reported in 4-10% of the adult population and negatively affects quality of life [1-5]. Diagnosing and managing CC is challenging [3-5]. Initial evaluation typically includes chest radiography, spirometry, blood cell count (to detect blood eosinophils) and exhaled nitric oxide fraction, if available [4, 5]. Further diagnostic tests are warranted if clinical symptoms and basic tests cannot identify the cause of CC. Secondary diagnostic tests include oesophageal manometry or pH/impedance monitoring, induced sputum for eosinophils, laryngoscopy, bronchial provocation challenge, chest computed tomography (CT) and bronchoscopy [3-5].

The spectrum, clinical features and diagnosis of chronic cough due to rare causes

Background

Chronic cough has many diverse causes, including common and uncommon causes. There are few comprehensive reports on rare causes of chronic cough. The purpose of this study is to determine the etiological distribution, clinical features, and diagnostic value of special examinations in patients with rare causes of chronic cough.

Methods

A retrospective analysis of patients with chronic cough who underwent medical history taking, full examination, and etiological treatment over a 13-year period was conducted. Causes of chronic cough with a prevalence of less than 3% were defined as rare causes.

Results

A total of 1,554 patients were enrolled, and 39 causes of chronic cough were identified. Among them, 1,055 cases were due to common causes, whereas 235 cases were due to rare causes; the causes involved 7 bodily systems. The top five rare causes were protracted bacterial bronchitis, somatic cough syndrome, diffuse panbronchiolitis, obstructive sleep apnea syndrome (OSAS), and interstitial lung disease, accounting for 67.2% of all rare causes. Among 235 patients with rare causes, causes in 90 (38.3%) patients were detected by chest high-resolution computed tomography (HRCT), in 44 (18.7%) patients by bronchoscopy/nasopharyngoscopy, and in 21 (8.9%) patients by pulmonary spirometry and diffusing capacity testing.

Conclusions

Among the 31 rare causes of chronic cough in this cohort, the top five were protracted bacterial bronchitis, somatic cough syndrome, diffuse panbronchiolitis, OSAS, and interstitial lung disease. Special examinations, such as chest HRCT and bronchoscopy, should be considered after excluding common causes of chronic cough.

Peripheral blood gene expression profiles in COPD subjects

To identify non-invasive gene expression markers for chronic obstructive pulmonary disease (COPD), we performed genome-wide expression profiling of peripheral blood samples from 12 subjects with significant airflow obstruction and an equal number of non-obstructed controls. RNA was isolated from Peripheral Blood Mononuclear Cells (PBMCs) and gene expression was assessed using Affymetrix U133 Plus 2.0 arrays.

Tests for gene expression changes that discriminate between COPD cases (FEV₁< 70% predicted, FEV₁/FVC < 0.7) and controls (FEV₁> 80% predicted, FEV₁/FVC > 0.7) were performed using Significance Analysis of Microarrays (SAM) and Bayesian Analysis of Differential Gene Expression (BADGE). Using either test at high stringency (SAM median FDR = 0 or BADGE p < 0.01) we identified differential expression for 45 known genes. Correlation of gene expression with lung function measurements (FEV₁ & FEV₁/FVC), using both Pearson and Spearman correlation coefficients (p < 0.05), identified a set of 86 genes. A total of 16 markers showed evidence of significant correlation (p < 0.05) with quantitative traits and differential expression between cases and controls. We further compared our peripheral gene expression markers with those we previously identified from lung tissue of the same cohort. Two genes, RP9and NAPE-PLD, were identified as decreased in COPD cases compared to controls in both lung tissue and blood. These results contribute to our understanding of gene expression changes in the peripheral blood of patients with COPD and may provide insight into potential mechanisms involved in the disease.