Multidetector Computed Tomographic Imaging in Chronic Obstructive Pulmonary Disease

Small airways disease in patients with alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder, characterized by panacinar emphysema mainly in the lower lobes, and predisposes to chronic obstructive pulmonary disease (COPD) at a younger age, especially in patients with concomitant cigarette smoking. Alpha-1 antitrypsin (a1-AT) is a serine protease inhibitor that mainly blocks neutrophil elastase and maintains protease/antiprotease balance in the lung and AATD is caused by mutations in the SERPINA1 gene that encodes a1-AT protein. PiZZ is the most common genotype associated with severe AATD, leading to reduced circulating levels of a1-AT. Besides its antiprotease function, a1-AT has anti-inflammatory and antioxidative effects and AATD results in defective innate immunity. Protease/antiprotease imbalance affects not only the lung parenchyma but also the small airways and recent studies have shown that AATD is associated with small airway dysfunction. Alterations in small airways structure with peripheral ventilation inhomogeneities may precede emphysema formation, providing a unique opportunity to detect early disease. The aim of the present review is to summarize the current evidence for the contribution of small airways disease in AATD-associated lung disease.

Seven Pillars of Small Airways Disease in Asthma and COPD: Supporting Opportunities for Novel Therapies

Identification of pathologic changes in early and mild obstructive lung disease has shown the importance of the small airways and their contribution to symptoms. Indeed, significant small airways dysfunction has been found prior to any overt airway obstruction being detectable by conventional spirometry techniques. However, most therapies for the treatment of obstructive lung disease target the physiological changes and associated symptoms that result from chronic lung disease, rather than directly targeting the specific underlying causes of airflow disruption or the drivers of disease progression. In addition, although spirometry is the current standard for diagnosis and monitoring of response to therapy, the most widely used measure, FEV1 , does not align with the pathologic changes in early or mild disease and may not align with symptoms or exacerbation frequency in the individual patient. Newer functional and imaging techniques allow more effective assessment of small airways dysfunction; however, significant gaps in our understanding remain. Improving our knowledge of the role of small airways dysfunction in early disease in the airways, along with the identification of novel end points to measure subclinical changes in this region (ie, those not captured as symptoms or identified through standard FEV1), may lead to the development of novel therapies that directly combat early airways disease processes with a view to slowing disease progression and reversing damage. This expert opinion paper discusses small airways disease in the context of asthma and COPD and highlights gaps in current knowledge that impede earlier identification of obstructive lung disease and the development and standardization of novel small airways-specific end points for use in clinical trials.

Appropriateness and clinical outcome of chest computed tomography without intravenous contrast: A study conducted in Pakistan

BACKGROUND

Chest computed tomography (CT), including high-resolution CT (HRCT), has become an integral part of modern healthcare. It enables the physician to arrive at a diagnosis using a noninvasive approach. Our practice has shown that various chest CT scans without intravenous (IV) contrast, including HRCT, have no proper clinical indication. For the same reason, we have assessed the appropriateness of chest CT without IV contrast based on the evidence-based American College of Radiology (ACR) appropriateness criteria.

METHODS

Chest CT scans without IV contrast were reviewed to evaluate if the examination was based upon the evidence-based ACR appropriateness criteria. All clinical indications, positive physical examination findings, laboratory test findings, and radiological records submitted at the time of chest CT were reviewed.

RESULTS

Of 1205 CT scans, 538 (44.6%) were considered "inappropriate," 367 (30.4%) were considered "appropriate," and 300 (24.8%) were considered "may be appropriate." CT scans were performed on 241 (20.0%) patients with no clinical history, whereas 148 (12.3%) examinations in patients aged < 40 years were performed with no positive physical finding. Positive results that affected the management were 4.43 times more likely to be considered appropriate than inappropriate (adjusted odds ratio, 4.43; 95% confidence interval, 1.81-10.87).

CONCLUSIONS

This study showed a high percentage of chest CT scans without IV contrast examinations not meeting the ACR appropriateness criteria. Chest CT is a valuable tool for evaluation of chest diseases only in the presence of adequate detailed history and physical examination.

Pulmonary quantitative CT imaging in focal and diffuse disease: current research and clinical applications

The frenetic development of imaging technology-both hardware and software-provides exceptional potential for investigation of the lung. In the last two decades, CT was exploited for detailed characterization of pulmonary structures and description of respiratory disease. The introduction of volumetric acquisition allowed increasingly sophisticated analysis of CT data by means of computerized algorithm, namely quantitative CT (QCT). Hundreds of thousands of CTs have been analysed for characterization of focal and diffuse disease of the lung. Several QCT metrics were developed and tested against clinical, functional and prognostic descriptors. Computer-aided detection of nodules, textural analysis of focal lesions, densitometric analysis and airway segmentation in obstructive pulmonary disease and textural analysis in interstitial lung disease are the major chapters of this discipline. The validation of QCT metrics for specific clinical and investigational needs prompted the translation of such metrics from research field to patient care. The present review summarizes the state of the art of QCT in both focal and diffuse lung disease, including a dedicated discussion about application of QCT metrics as parameters for clinical care and outcomes in clinical trials.

Lung cancer screening with low-dose CT in Europe: strength and weakness of diverse independent screening trials

A North American trial reported a significant reduction of lung cancer mortality and overall mortality as a result of annual screening using low-dose computed tomography (LDCT). European trials prospectively tested a variety of possible screening strategies. The main topics of current discussion regarding the optimal screening strategy are pre-test selection of the high-risk population, interval length of LDCT rounds, definition of positive finding, and post-test apportioning of lung cancer risk based on LDCT findings. Despite the current lack of statistical evidence regarding mortality reduction, the European independent diverse strategies offer a multi-perspective view on screening complexity, with remarkable indications for improvements in cost-effectiveness and harm-benefit balance. The UKLS trial reported the advantage of a comprehensive and simple risk model for selection of patients with 5% risk of lung cancer in 5 years. Subjective risk prediction by biological sampling is under investigation. The MILD trial reported equal efficiency for biennial and annual screening rounds, with a significant reduction in the total number of LDCT examinations. The NELSON trial introduced volumetric quantification of nodules at baseline and volume-doubling time (VDT) for assessment of progression. Post-test risk refinement based on LDCT findings (qualitative or quantitative) is under investigation. Smoking cessation remains the most appropriate strategy for mortality reduction, and it must therefore remain an integral component of any lung cancer screening programme.

Clinical-Radiologic-Pathologic Correlation of Smoking-Related Diffuse Parenchymal Lung Disease

The direct toxicity of cigarette smoke and the body's subsequent response to this lung injury leads to a wide array of pathologic manifestations and disease states that lead to both reversible and irreversible injury to the large airways, small airways, alveolar walls, and alveolar spaces. These include emphysema, bronchitis, bronchiolitis, acute eosinophilic pneumonia, pulmonary Langerhans cell histiocytosis, respiratory bronchiolitis, desquamative interstitial pneumonia, and pulmonary fibrosis. Although these various forms of injury have different pathologic and imaging manifestations, they are all part of the spectrum of smoking-related diffuse parenchymal lung disease.

Chronic Obstructive Pulmonary Disease: Pulmonary Function and CT Lung Attenuation Do Not Show Linear Correlation

PURPOSE

To determine whether the relationship between pulmonary function and computed tomographic (CT) lung attenuation in chronic obstructive pulmonary disease (COPD), which is traditionally described with single univariate and multivariate statistical models, could be more accurately described with a multiple model estimation approach.

MATERIALS AND METHODS

The study was approved by the local ethics committee. All participants provided written informed consent. The prediction of the percentage area with CT attenuation values less than -950 HU at inspiration (%LAA-950insp) and less than -910 HU at expiration (%LAA-910exp) obtained with single univariate and multivariate models was compared with that obtained with a multiple model estimation approach in 132 patients with COPD.

RESULTS

At univariate analysis, %LAA-950insp and %LAA-910exp values higher than the mean value of this cohort (19.1% and 22.0%) showed better correlation with percentage of predicted diffusing capacity of lung for carbon monoxide (Dlco%) than with airflow obstruction (forced expiratory volume in 1 second [FEV1]/vital capacity [VC]). Conversely, %LAA-950insp and %LAA-910exp values lower than the mean value were correlated with FEV1/VC but not with Dlco%. Multiple model estimation performed with two multivariate regressions, each selecting the most appropriate functional variables (FEV1/VC for mild parenchymal destruction, Dlco% and functional residual capacity for severe parenchymal destruction), predicted better than single multivariate regression both %LAA-950insp (R(2) = 0.75 vs 0.46) and %LAA-910exp (R(2) = 0.83 vs 0.63).

CONCLUSION

The relationship between pulmonary function data and CT densitometric changes in COPD varies with the level of lung attenuation impairment. The nonlinear profile of this relationship is accurately predicted with a multiple model estimation approach.

Biomarkers of progression of chronic obstructive pulmonary disease (COPD)

Disease progression of chronic obstructive pulmonary disease (COPD) is variable, with some patients having a relatively stable course, while others suffer relentless progression leading to severe breathlessness, frequent acute exacerbations of COPD (AECOPD), respiratory failure and death. Radiological markers such as CT emphysema index, bronchiectasis and coronary artery calcification (CAC) have been linked with increased mortality in COPD patients. Molecular changes in lung tissue reflect alterations in lung pathology that occur with disease progression; however, lung tissue is not routinely accessible. Cell counts (including neutrophils) and mediators in induced sputum have been associated with lung function and risk of exacerbations. Examples of peripheral blood biological markers (biomarkers) include those associated with lung function (reduced CC-16), emphysema severity (increased adiponectin, reduced sRAGE), exacerbations and mortality [increased CRP, fibrinogen, leukocyte count, IL-6, IL-8, and tumor necrosis factor α (TNF-α)] including increased YKL-40 with mortality. Emerging approaches to discovering markers of gene-environment interaction include exhaled breath analysis [volatile organic compounds (VOCs), exhaled breath condensate], cellular and systemic responses to exposure to air pollution, alterations in the lung microbiome, and biomarkers of lung ageing such as telomere length shortening and reduced levels of sirtuins. Overcoming methodological challenges in sampling and quality control will enable more robust yet easily accessible biomarkers to be developed and qualified, in order to optimise personalised medicine in patients with COPD.