Maximal mid-expiratory flow is a surrogate marker of lung clearance index for assessment of adults with bronchiectasis

Research advances and clinical management of bronchiectasis: Chinese perspective

Bronchiectasis is a debilitating chronic suppurative airway disease that confers a substantial burden globally. Despite the notable prevalence, research on bronchiectasis in mainland China remains in its infancy. Nevertheless, there has been a significant leap in the quantity and quality of research, which has contributed to the ever-improving clinical practice. A nationwide collaborative platform has been established to foster multicentre studies, which will help increase the level of evidence further. Here, we summarise the status quo of clinical management and consider the research priorities for bronchiectasis that have been published previously. We also highlight the efforts of the Chinese medical communities to outline the core tasks that need to be addressed within the next decade.

Diagnosis and quantification of bronchiectasis using computed tomography or magnetic resonance imaging: A systematic review

BACKGROUND

Bronchiectasis is an irreversible dilatation of the airways caused by inflammation and infection. To diagnose bronchiectasis in clinical care and to use bronchiectasis as outcome parameter in clinical trials, a radiological definition with exact cut-off values along with image analysis methods to assess its severity are needed. The aim of this study was to review diagnostic criteria and quantification methods for bronchiectasis.

METHODS

A systematic literature search was performed using Embase, Medline Ovid, Web of Science, Cochrane and Google Scholar. English written, clinical studies that included bronchiectasis as outcome measure and used image quantification methods were selected. Criteria for bronchiectasis, quantification methods, patient demographics, and data on image acquisition were extracted.

RESULTS

We screened 4182 abstracts, selected 972 full texts, and included 122 studies. The most often used criterion for bronchiectasis was an inner airway-artery ratio ≥1.0 (42%), however no validation studies for this cut-off value were found. Importantly, studies showed that airway-artery ratios are influenced by age. To quantify bronchiectasis, 42 different scoring methods were described.

CONCLUSION

Different diagnostic criteria for bronchiectasis are being used, but no validation studies were found to support these criteria. To use bronchiectasis as outcome in future studies, validated and age-specific cut-off values are needed.

Ambient PM2.5 causes lung injuries and coupled energy metabolic disorder

Ambient fine particulate matter (PM_2.5) is a challenge to public health worldwide. Although increasing numbers of recent epidemiological studies have emphasized the critical role of PM_2.5 in promoting respiratory diseases, the precise mechanism behind PM_2.5-mediated lung obstruction remains obscure. In the present study, we analyzed lung structure and function and further investigated mitochondrial morphology and transcription-modulated energy metabolism in mice following PM_2.5 aspiration. The results showed that PM_2.5 exposure reduced pulmonary function and induced severe pathological alterations, including alveolar endothelial disruption and airway obstruction. Based on ultrastructural observations, we also found mitochondrial vacuolation and mitochondrial membrane rupture in alveolar type II epithelial cells. Importantly, the abnormality of mitochondrial structure was coupled with energy metabolism disorders, as evidenced by the decrease in ATP levels, the accumulation of pyruvate and lactate content, and the altered transcription of related genes. Moreover, the reduction in mitochondrial markers, including PGC-1α, NRF-1, and TFAM, were involved in mitochondrial dysfunction. These findings suggest that energy metabolic disorders and mitochondrial dysfunction may be the important contributors to pulmonary injuries in response to PM_2.5 exposure, indicating possible targets for protection and therapy in polluted areas.

Next-generation sequencing for identifying genetic mutations in adults with bronchiectasis

BACKGROUND

Defective airway host-defense (e.g., altered mucus properties, ciliary defects) contributes to the pathogenesis of bronchiectasis. This study aims to determine whether genetic mutations associated with defective airway host-defense are implicated in the pathogenesis of bronchiectasis.

METHODS

Based on the systematic screening of 32 frequently reported bronchiectasis-associated genes, we performed next-generation sequencing (NGS) on peripheral blood samples from 192 bronchiectasis patients and 100 healthy subjects. The variant distribution frequency and pathogenicity of mutations were analyzed.

RESULTS

We identified 162 rare variants in 192 bronchiectasis patients, and 85 rare variants among 100 healthy subjects. Among bronchiectasis patients, 25 (15.4%), 117 (72.2%) and 18 (11.1%) rare variants were associated with cystic fibrosis transmembrane receptor (CFTR), epithelial sodium channel, and primary ciliary dyskinesia genes, respectively. Biallelic CFTR variants were detected in four bronchiectasis patients but none of the healthy subjects. Carriers of homozygous p.M470 plus at least one CFTR rare variant were detected in 6.3% of bronchiectasis patients (n=12) and in 1.0% of healthy subjects (n=1, P=0.039). Twenty-six patients (16 with idiopathic and 6 with post-infectious bronchiectasis) harbored biallelic variants. Bronchiectasis patients with biallelic DNAH5 variants, or biallelic CFTR variants plus an epithelial sodium channel variant, tended to have greater disease severity.

CONCLUSIONS

Genetic mutations leading to impaired host-defense might have implicated in the pathogenesis of bronchiectasis. Genetic screening may be a useful tool for unraveling the underlying causes of bronchiectasis, and offers molecular information which is complementary to conventional etiologic assessment for bronchiectasis.

Residual volume/total lung capacity ratio confers limited additive significance to lung clearance index for assessment of adults with bronchiectasis

BACKGROUND

Mosaicism and hyperinflation are common pathophysiologic features of bronchiectasis. The magnitude of ventilation heterogeneity might have been affected by the degree of hyperinflation. Some studies have evaluated the discriminative performance of lung clearance index (LCI) in bronchiectasis patients, but the additive diagnostic value of hyperinflation metrics to LCI is unknown.

OBJECTIVE

To compare LCI and the ratio of residual volume to total lung capacity (RV/TLC), along with the LCI normalized with RV/TLC, in terms of discriminative performance, correlation and concordance with clinical variables in adults with bronchiectasis.

METHODS

Measurement items included chest high-resolution computed tomography, multiple-breath nitrogen washout test, spirometry, and sputum culture. We analyzed bronchodilator responses by stratifying LCI and RV/TLC according to their median levels (LCIHigh/RV/TLCHigh, LCILow/RV/TLCHigh, LCIHigh/RV/TLCLow, and LCILow/RV/TLCLow).

RESULTS

Data from 127 adults with clinically stable bronchiectasis were analyzed. LCI had greater diagnostic value than RV/TLC in discriminating moderate-to-severe from mild bronchiectasis, had greater concordance in reflecting clinical characteristics (including the number of bronchiectatic lobes, radiological severity score, and the presence of cystic bronchiectasis). Normalization of LCI with RV/TLC did not contribute to greater discriminative performance or concordance with clinical variables. The LCI, before and after normalization with RV/TLC, correlated statistically with age, sex, HRCT score, Pseudomonas aeruginosa colonization, cystic bronchiectasis, and ventilation heterogeneity (all P<0.05). Different bronchodilator responses were not significant among the four subgroups of bronchiectasis patients, including those with discordant LCI and RV/TLC levels.

CONCLUSION

LCI is superior to RV/TLC for bronchiectasis assessment. Normalization with RV/TLC is not required. Stratification of LCI and RV/TLC is not associated with significantly different bronchodilator responses.

Patients hospitalized with an infective exacerbation of bronchiectasis unrelated to cystic fibrosis: Clinical, physiological and sputum characteristics

BACKGROUND AND OBJECTIVE

Bronchiectasis is a growing health burden both globally and in Australasia. Associated with repeated respiratory infections, the disease often results in hospital admission, impaired quality of life, reduced lung function and shortened life expectancy. We describe the local clinical, physiological and sputum characteristics in patients hospitalized with an infective exacerbation of bronchiectasis.

METHODS

This study examined the medical records of all 61 adults admitted to a metropolitan Australian hospital with an infective exacerbation of bronchiectasis in a calendar year.

RESULTS

Baseline characteristics include: mean (SD) age of participants was 66 (14) years; 56% were women and 42% were current or ex-smokers. The majority had other coexisting medical conditions, with asthma in 44%, COPD in 59% and both asthma and COPD in 31%. Seventy-two percent were on regular inhaled medication, 23% on cyclical antibiotics and 26% undertook regular respiratory physiotherapy. Bronchodilator reversibility was present in 17% and small airway reversibility in 41%. Sputum demonstrated normal flora in 17%, Pseudomonas aeruginosa in 32%, Haemophilus influenzae in 15% and both organisms in 17%. Mean numbers of exacerbations per year requiring hospitalization was 2.3. Sixty-two percent of subjects had an Index of Relative Socio-Economic Disadvantage in deciles 1-5. Risk factors for exacerbations included a history of asthma or COPD, documented small airway reversibility and presence of P. aeruginosa.

CONCLUSION

Patients hospitalized with an infective exacerbation of bronchiectasis are predominantly older with co-morbidities and of lower socio-economic status. Presence of P. aeruginosa was a risk factor for repeated exacerbations, as was a history of asthma, COPD or small airway reversibility.