Computed tomographic-based quantification of emphysema and correlation to pulmonary function and mechanics

High Blood Eosinophil Count at Stable State is Not Associated with Airway Microbiota Distinct Profile in COPD

Purpose

The heterogeneity of clinical features in COPD at stable state has been associated with airway microbiota. Blood eosinophil count (BEC) represents a biomarker for a pejorative evolution of COPD, including exacerbations and accelerated FEV1 decline. We aimed to analyse the associations between BEC and airway microbiota in COPD at stable state.

Patients and Methods

Adult COPD patients at stable state (RINNOPARI cohort) were included and characterised for clinical, functional, biological and morphological features. BEC at inclusion defined 2 groups of patients with low BEC <300/mm3 and high BEC ≥300/mm3. Sputa were collected and an extended microbiological culture was performed for the identification of viable airway microbiota.

Results

Fifty-nine subjects were included. When compared with the low BEC (n=40, 67.8%), the high BEC group (n=19, 32.2%) had more frequent exacerbations (p<0.001) and more pronounced cough and sputum (p<0.05). The global composition, the number of bacteria per sample and the α-diversity of the microbiota did not differ between groups, as well as the predominant phyla (Firmicutes), or the gender repartition.

Conclusion

In our study, high BEC in COPD at stable state was associated with a clinical phenotype including frequent exacerbation, but no distinct profile of viable airway microbiota compared with low BEC.

Topologic Parametric Response Mapping Identifies Tissue Subtypes Associated with Emphysema Progression

RATIONALE AND OBJECTIVES

Small airways disease (SAD) and emphysema are significant components of chronic obstructive pulmonary disease (COPD), a heterogenous disease where predicting progression is difficult. SAD, a principal cause of airflow obstruction in mild COPD, has been identified as a precursor to emphysema. Parametric Response Mapping (PRM) of chest computed tomography (CT) can help distinguish SAD from emphysema. Specifically, topologic PRM can define local patterns of both diseases to characterize how and in whom COPD progresses. We aimed to determine if distribution of CT-based PRM of functional SAD (fSAD) is associated with emphysema progression.

MATERIALS AND METHODS

We analyzed paired inspiratory-expiratory chest CT scans at baseline and 5-year follow up in 1495 COPDGene subjects using topological analyses of PRM classifications. By spatially aligning temporal scans, we mapped local emphysema at year five to baseline lobar PRM-derived topological readouts. K-means clustering was applied to all observations. Subjects were subtyped based on predominant PRM cluster assignments and assessed using non-parametric statistical tests to determine differences in PRM values, pulmonary function metrics, and clinical measures.

RESULTS

We identified distinct lobar imaging patterns and classified subjects into three radiologic subtypes: emphysema-dominant (ED), fSAD-dominant (FD), and fSAD-transition (FT: transition from healthy lung to fSAD). Relative to year five emphysema, FT showed rapid local emphysema progression (-57.5% ± 1.1) compared to FD (-49.9% ± 0.5) and ED (-33.1% ± 0.4). FT consisted primarily of at-risk subjects (roughly 60%) with normal spirometry.

CONCLUSION

The FT subtype of COPD may allow earlier identification of individuals without spirometrically-defined COPD at-risk for developing emphysema.

Bronchoscopic lung volume reduction by instillation of fibrinogen and thrombin in COPD patients with homogenous emphysema

BACKGROUND

The new endobronchial therapy called biological lung volume reduction (BioLVR) involves using a rapid polymerizing sealant to block off the most emphysematous portions of the lungs. The primary mechanism of action is resorption atelectasis, which is then followed by inflammation and remodeling of the airspace. The remodeling process will result in the formation of scars, leading to the contraction of the lung tissue. As a result, a decrease in functional lung volume is anticipated for a period of 6-8 weeks.

OBJECTIVE

Assessing the safety and effectiveness of bronchoscopic installation of (fibrinogen and thrombin) in COPD patients with homogeneous emphysema in terms of radiological, physiological, and quality of life outcomes.

METHODS

Between December 2017 and December 2019, 40 COPD patients with homogeneous emphysema were studied using a fiber optic bronchoscope while they were awake but sedated. Tanta University Hospitals' chest medicine department collaborated with the diagnostic radiology department of the Faculty of Medicine.

RESULTS

All the following parameters were reduced from their initial values: HRCT volumetry, RV/TLC, mMRC dyspnea scale, CAT score, 6MWT, FEV1, and the FEV1/FVC ratio at the first, third, and sixth months from the beginning (p = 0.001). One individual (0.025%) had pneumonia, whereas three individuals had COPD (0.075%). Using fibrin glue produced locally, biological lung volume reduction (Bio LVR) may be an effective treatment for advanced homogenous emphysema.

CONCLUSION

By using locally prepared fibrin glue the biologic lung volume reduction (Bio LVR) may be a convenient method to treat advanced homogenous emphysema.

CT-based emphysema characterization per lobe: A proof of concept

PURPOSE

The Fleischner society criteria are global criteria to visually evaluate and classify pulmonary emphysema on CT. It may group heterogeneous disease severity within the same category, potentially obscuring clinically relevant differences in emphysema severity. This proof-of-concept study proposes to split emphysema into more categories and to assess each lobe separately, and applies this to two general population-based cohort samples to assess what information such an extension adds.

METHOD

From a consecutive sample in two general population-based cohorts with low-dose chest CT, 117 participants with more than a trace of emphysema were included. Two independent readers performed an extended per-lobe classification and assessed overall severity semi-quantitatively. An emphysema sum score was determined by adding the severity score of all lobes. Inter-reader agreement was quantified with Krippendorff Alpha.

RESULTS

Based on Fleischner society criteria, 69 cases had mild to severe centrilobular emphysema, and 90 cases had mild or moderate paraseptal emphysema (42 had both types of emphysema). The emphysema sum score was significantly different between mild (10.7 ± 4.3, range 2-22), moderate (20.1 ± 3.1, range: 15-24), and severe emphysema (23.6 ± 3.4, range: 17-28, p < 0.001), but ranges showed significant overlap. Inter-reader agreement for the extended classification and sum score was substantial (alpha 0.79 and 0.85, respectively). Distribution was homogenous across lobes in never-smokers, yet heterogenous in current smokers, with upper-lobe predominance.

CONCLUSIONS

The proposed emphysema evaluation method adds information to the original Fleischner society classification. Individuals in the same Fleischner category have diverse emphysema sum scores, and lobar emphysema distribution differs between smoking groups.

Quantitative CT parameters correlate with lung function in chronic obstructive pulmonary disease: A systematic review and meta-analysis

Objective

This study aimed to analyze the correlation between quantitative computed tomography (CT) parameters and airflow obstruction in patients with COPD.

Methods

PubMed, Embase, Cochrane and Web of Knowledge were searched by two investigators from inception to July 2022, using a combination of pertinent items to discover articles that investigated the relationship between CT measurements and lung function parameters in patients with COPD. Five reviewers independently extracted data, and evaluated it for quality and bias. The correlation coefficient was calculated, and heterogeneity was explored. The following CT measurements were extracted: percentage of lung attenuation area <-950 Hounsfield Units (HU), mean lung density, percentage of airway wall area, air trapping index, and airway wall thickness. Two airflow obstruction parameters were extracted: forced expiratory volume in the first second as a percentage of prediction (FEV₁%pred) and FEV₁ divided by forced expiratory volume lung capacity.

Results

A total of 141 studies (25,214 participants) were identified, which 64 (6,341 participants) were suitable for our meta-analysis. Results from our analysis demonstrated that there was a significant correlation between quantitative CT parameters and lung function. The absolute pooled correlation coefficients ranged from 0.26 (95% CI, 0.18 to 0.33) to 0.70 (95% CI, 0.65 to 0.75) for inspiratory CT and 0.56 (95% CI, 0.51 to 0.60) to 0.74 (95% CI, 0.68 to 0.80) for expiratory CT.

Conclusions

Results from this analysis demonstrated that quantitative CT parameters are significantly correlated with lung function in patients with COPD. With recent advances in chest CT, we can evaluate morphological features in the lungs that cannot be obtained by other clinical indices, such as pulmonary function tests. Therefore, CT can provide a quantitative method to advance the development and testing of new interventions and therapies for patients with COPD.

Extended Bacteria Culture-Based Clustering Identifies a Phenotype Associating Increased Cough and Enterobacterales in Stable Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory lung disease characterized by airflow limitation. This chronic respiratory disease represents the third leading cause of death worldwide. Alteration of the airway microbiota has been reported to be associated with exacerbation frequency in COPD, but its role on the symptoms in patients at stable state is still incompletely described. This study aimed to determine whether bacteria isolated in sputum can be associated with the clinical features of COPD patients within stable state. Our study highlights, for the first time, that altered microbiota with Enterobacterales is associated with pejorative clinical symptoms in stable COPD patients. The airway microbiota of 38 patients was analyzed using an extended culture approach and mass spectrometry identification. Cluster analysis by principal coordinate analysis of the bacterial communities showed that the patients could be classified into three distinct clusters in our cohort. The clusters showed no differences in proportions of the phylum, but one of them was associated with a high prevalence of Enterobacterales (71.4% in cluster 1 vs. 0% in cluster 3), loss of microbiota diversity, and higher bacterial load (10⁷ vs. 10⁵ CFU/ml, respectively) and characterized by predominant cough and impact on mental health. These novel findings, supported by further studies, could lead to modifying the processing of COPD sputum in the everyday practice of clinical microbiology laboratories.

3D Oxygen-Enhanced MRI at 3T MR System: Comparison With Thin-Section CT of Quantitative Capability for Pulmonary Functional Loss Assessment and Clinical Stage Classification of COPD in Smokers

BACKGROUND

Oxygen (O₂ )-enhanced MRI is mainly performed by a 2D sequence using 1.5T MR systems but trying to be obtained by a 3D sequence using a 3T MR system.

PURPOSE

To compare the capability of 3D O₂ -enhanced MRI and that of thin-section computed tomography (CT) for pulmonary functional loss assessment and clinical stage classification of chronic obstructive pulmonary disease (COPD) in smokers.

STUDY TYPE

Prospective study.

POPULATION

Fifty six smokers were included.

FIELD STRENGTH/ SEQUENCE

3T, 3D O₂ -enhanced MRIs were performed with a 3D T₁ -weighted fast field echo pulse sequence using the multiple flip angles.

ASSESSMENTS

Smokers were classified into four stages ("Without COPD," "Mild COPD," "Moderate COPD," "Severe or very severe COPD"). Maps of regional changes in T₁ values were generated from O₂ -enhanced MR data. Regions of interest (ROIs) were then placed over the lung on all slices and averaged to determine mean T₁ value change (ΔT₁ ). Quantitative CT used the percentage of low attenuation areas within the entire lung (LAA%).

STATISTICAL TESTS

ΔT₁ and LAA% were correlated with pulmonary functional parameters, and compared for four stages using Tukey's Honestly Significant Difference test. Discrimination analyses were performed and McNemar's test was used for a comparison of the accuracy of the indexes.

RESULTS

There were significantly higher correlations between ΔT₁ and pulmonary functional parameters (-0.83 ≤ r ≤ -0.71, P < 0.05) than between LAA% and the same pulmonary functional parameters (-0.76 ≤ r ≤ -0.69, P < 0.05). ΔT₁ and LAA% of the "Mild COPD" and "Moderate COPD" groups were significantly different from those of the "Severe or Very Severe COPD" group (P < 0.05). Discriminatory accuracy of ΔT₁ (62.5%) and ΔT1 with LAA% (67.9%) was significantly greater than that of LAA% (48.2%, P < 0.05).

DATA CONCLUSION

Compared with thin-section CT, 3D O₂ -enhanced MRI has a similar capability for pulmonary functional assessment but better potential for clinical stage classification in smokers.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 1.

Multi-Reader-Multi-Split Annotation of Emphysema in Computed Tomography

Emphysema is visible on computed tomography (CT) as low-density lesions representing the destruction of the pulmonary alveoli. To train a machine learning model on the emphysema extent in CT images, labeled image data is needed. The provision of these labels requires trained readers, who are a limited resource. The purpose of the study was to test the reading time, inter-observer reliability and validity of the multi-reader-multi-split method for acquiring CT image labels from radiologists. The approximately 500 slices of each stack of lung CT images were split into 1-cm chunks, with 17 thin axial slices per chunk. The chunks were randomly distributed to 26 readers, radiologists and radiology residents. Each chunk was given a quick score concerning emphysema type and severity in the left and right lung separately. A cohort of 102 subjects, with varying degrees of visible emphysema in the lung CT images, was selected from the SCAPIS pilot, performed in 2012 in Gothenburg, Sweden. In total, the readers created 9050 labels for 2881 chunks. Image labels were compared with regional annotations already provided at the SCAPIS pilot inclusion. The median reading time per chunk was 15 s. The inter-observer Krippendorff's alpha was 0.40 and 0.53 for emphysema type and score, respectively, and higher in the apical part than in the basal part of the lungs. The multi-split emphysema scores were generally consistent with regional annotations. In conclusion, the multi-reader-multi-split method provided reasonably valid image labels, with an estimation of the inter-observer reliability.

Translation of adapting quantitative CT data from research to local clinical practice: validation evaluation of fully automated procedures to provide lung volumes and percent emphysema

Current clinical chest CT reporting includes limited qualitative assessment of emphysema with rare mention of lung volumes and limited reporting of emphysema, based upon retrospective review of CT reports. Quantitative CT analysis performed in COPDGene and other research cohorts utilize semiautomated segmentation procedures and well-established research method (Thirona). We compared this reference QCT data with fully automated QCT analysis that can be obtained at the time of CT scan and sent to PACS along with standard chest CT images. 164 COPDGene^® cohort study subjects enrolled at Brigham and Women's Hospital had baseline and 5-year follow-up CT scans. Subjects included 17 nonsmoking controls, 92 smokers with normal spirometry, 15 preserved ratio impaired spirometry (PRISm) patients, 12 GOLD 1, 20 GOLD 2, and 8 GOLD 3-4. 97% ( n = 319 ) of clinical reports did not mention lung volumes, and 14% ( n = 46 ) made no mention of emphysema. Total lung volumes determined by the fully automated algorithm were consistently 47 milliliters (ml) less than the Thirona reference value for all subjects (95% confidence interval - 62 to - 32    ml ). Percent emphysema values were equivalent to the Thirona reference values. Well-established research reference data can be used to evaluate and validate automated QCT software. Validation can be repeated as software is updated.

Brief Report: Systemic Inflammation, Immune Activation, and Impaired Lung Function Among People Living With HIV in Rural Uganda

BACKGROUND

Although both chronic lung disease and HIV are inflammatory diseases common in sub-Saharan Africa, the relationship between systemic inflammation and lung function among people living with HIV (PLWH) in sub-Saharan Africa is not well described.

METHODS

We measured lung function (using spirometry) and serum high sensitivity C-reactive protein, interleukin 6 (IL-6), soluble CD14 (sCD14), and soluble CD163 (sCD163) in 125 PLWH on stable antiretroviral therapy (ART) and 109 age- and sex-similar HIV-uninfected control subjects in rural Uganda. We modeled the relationship between lung function and systemic inflammation using linear regression, stratified by HIV serostatus, controlled for age, sex, height, tobacco, and biomass exposure.

RESULTS

Half of subjects [46% (107/234)] were women, and the median age was 52 years (interquartile range: 48-55). Most PLWH [92% (115/125)] were virologically suppressed on first-line ART. Median CD4 count was 472 cells/mm. In multivariable linear regression models stratified by HIV serostatus, an interquartile range increase in IL-6 and sCD163 were each inversely associated with lung function (mL, 95% confidence interval) among PLWH [IL-6: forced expiratory volume in 1 second (FEV1) -18.1 (-29.1 to -7.1), forced vital capacity (FVC) -17.1 (-28.2 to -5.9); sCD163: FVC -14.3 (-26.9 to -1.7)]. High sensitivity C-reactive protein (>3 vs. <1 mg/L) was inversely associated with lung function among both PLWH and HIV-uninfected control subjects [PLWH: FEV1 -39.3 (-61.7 to -16.9), FVC -44.0 (-48.4 to -6.4); HIV-uninfected: FEV1 -37.9 (-63.2 to -12.6), FVC -58.0 (-88.4 to -27.5)]. sCD14 was not associated with lung function, and all interaction terms were insignificant.

CONCLUSIONS

Macrophage activation and systemic inflammation are associated with lower lung function among PLWH on stable ART in rural Uganda. Future work should focus on underlying mechanisms and public health implications.

Prediction of response to endobronchial coiling based on morphologic emphysema characterization of the lung lobe to be treated and the ipsilateral non-treated lobe as well as on functional computed tomography-data: correlation with clinical and pulmonary function

Background

To test if the emphysema type of the targeted lobe, ipsilateral non-targeted lobe, and lobes of the contralateral lung impact outcome of endobronchial lung volume reduction (ELVR) treatment, and to document lobar volume changes in treated and non-treated lung lobes.

Methods

Thirty patients (16 men, 14 women; median age, 66±6 years; range, 48-78 years) underwent chest-computed tomography (CT) before and after endobronchial coiling for lung volume reduction (LVR) at our institution between December 2011 and March 2016. Forty-five pulmonary lobes were coiled. We classified the treated lobes into homogenous or heterogeneous emphysema phenotype based on the distribution of voxels showing tissue attenuation of less than -950 HU. Clinical response was defined as an increase or consistency in the walking distance (6MWT) 6 months after LVR-therapy. Lung volume changes were compared for treated, ipsilateral, and contralateral lobes. Additionally, pulmonary function tests (PFT), chronic obstructive pulmonary disease (COPD) assessment test (CAT), and blood gas analysis were performed.

Results

Responder (19/30, 63.3%) showed a significant improvement of 6 MWT from 281.05 to 335.26 (P=0.001). Non-responder (11/30, 36.7%) showed a decrease in 6MWT from 308.18 to 255.45 (P=0.001). Responders showed a significant reduction in CAT test from 23.23 to 20.73 points (P=0.038) and pCO₂ from 42.94 to 40.31 (P=0.001), whereas non-responders showed an increase in pCO₂ (P=0.003; from 44.27 to 47.45). There were no significant changes in PFT-parameters. In responders, there was a significant volume reduction in treated lobes from 1,627.68 to 1,519.21 mL (P=0.009). In responders, treated lobes/non-treated ipsilateral lobes were homogenous (n=11/5) and heterogeneous (n=10/28). In non-responders, treated lobes/non-treated ipsilateral were homogenous (n=5/4) and heterogeneous (n=7/16). In responders and non-responders, the emphysema phenotype in treated, ipsilateral non-treated and even contralateral lobes (P=0.250) did not differ and or change significantly before and after therapy. Only the volume of treated lobes in responders changed significantly after coiling.

Conclusions

The emphysema-phenotype in the targeted and non-targeted ipsilateral lobe has no impact on the outcome of endobronchial coiling for LVR and also does not change significantly after treatment, whereas the volume of the treated lobe significantly decreases in responders.

Staged unilateral lung volume reduction surgery: from mini-invasive to minimalist treatment strategies

Lung volume reduction surgery (LVRS) entailing unilateral or bilateral non-anatomical resection of severely damaged emphysematous tissue carried out by thoracoscopic or open surgical approaches, under general anesthesia with single-lung ventilation, has resulted in significant and long-lasting clinical and functional benefit. Unfortunately, the morbidity rates reported by simultaneous bilateral resectional LVRS has led to raise criticism regarding its cost-effectiveness and has stimulated in recent years the development of less invasive bronchoscopic and surgical non-resectional methods of treatment that are preferentially performed in a staged unilateral fashion. We had previously proposed an innovative LVRS modality, which did not entail any resection of lung tissue and was electively carried out according to a staged unilateral strategy by a multiport thoracoscopic access, through thoracic epidural anesthesia in conscious, spontaneously ventilating patients (awake LVRS). The awake LVRS resulted in significant clinical benefit paralleling that achieved by the resectional method with lower morbidity rates and shorter hospital stay. Moreover, the awake LVRS proved also suitable to be employed in stringently selected patients to perform redo procedures following previous successful bilateral LVRS. More recently, in order to minimize the global surgery- and anesthesia-related traumas, we have modified our original non-resectional method by adopting a single thoracoscopic access as well as an anesthesia protocol entailing use of a simple intercostal block with target control sedation, to realize an ultra-minimally invasive or minimalist LVRS. Hence, a deeper investigation of the pros and cons of staged unilateral LVRS strategies as well as of the novel surgical non-resectional and redo LVRS is warranted in order to verify, the optimal strategies of treatment, which will prove to reduce the typical LVRS-related morbidity while assuring the most durable benefit in patients with advanced emphysema.

Relationship of CT-quantified emphysema, small airways disease and bronchial wall dimensions with physiological, inflammatory and infective measures in COPD

BACKGROUND

COPD is a complex, heterogeneous disease characterised by progressive development of airflow limitation. Spirometry provides little information about key aspects of pathology and is poorly related to clinical outcome, so other tools are required to investigate the disease. We sought to explore the relationships between quantitative CT analysis with functional, inflammatory and infective assessments of disease to identify the utility of imaging to stratify disease to better predict outcomes and disease response.

METHODS

Patients from the AERIS study with moderate-very severe COPD underwent HRCT, with image analysis determining the quantity of emphysema (%LAA_<- 950), small airways disease (E/I MLD) and bronchial wall thickening (Pi10). At enrolment subjects underwent lung function testing, six-minute walk testing (6MWT), blood sampling for inflammatory markers and sputum sampling for white cell differential and microbiological culture and PCR.

RESULTS

122 subjects were included in this analysis. Emphysema and small airways disease had independent associations with airflow obstruction (β = - 0.34, p < 0.001 and β = - 0.56, p < 0.001). %LAA_<- 950 had independent associations with gas transfer (β = - 0.37, p < 0.001) and E/I MLD with RV/TLC (β = 0.30, p =0.003). The distance walked during the 6MWT was not associated with CT parameters, but exertional desaturation was independently associated with emphysema (β = 0.73, p < 0.001). Pi10 did not show any independent associations with lung function or functional parameters. No CT parameters had any associations with sputum inflammatory cells. Greater emphysema was associated with lower levels of systemic inflammation (CRP β = - 0.34, p < 0.001 and fibrinogen β = - 0.28, p =0.003). There was no significant difference in any of the CT parameters between subjects where potentially pathogenic bacteria were detected in sputum and those where it was not.

CONCLUSIONS

This study provides further validation for the use of quantitative CT measures of emphysema and small airways disease in COPD as they showed strong associations with pulmonary physiology and functional status. In contrast to this quantitative CT measures showed few convincing associations with biological measures of disease, suggesting it is not an effective tool at measuring disease activity.

Relationships between pulmonary function test parameters and quantitative computed tomography measurements of emphysema in subjects with chronic obstructive pulmonary disease

Objective.

CT is able to precisely define the pathological process in COPD. There are a number of previous articles discussing the distribution of emphysema and its connection with pulmonary function tests. However, the results obtained by the researchers are not identical.

Purpose.

To assess relationships between emphysema and pulmonary function test parameters in COPD patients.

Materials and methods.

Fifty-nine patients diagnosed to have COPD underwent chest CT examinations and pulmonary function tests.

For the quantitative assessment, percentages of low attenuation volume LAV _{950 HU} (%) of a both lungs, the right lung, the left lung, and each lobe were obtained. Quantitative CT measurements were compared with forced expiratory volume in 1 s (FEV₁), the ratio of FEV₁ to forced vital capacity (FEV₁/FVC), the diffusing capacity for carbon monoxide (DLco) and total lung capacity (TLC).

Results.

Except for the right middle lobe and the right upper lobe, respectively, all the quantitative CT measurements showed weak to moderate negative correlations with diffusing capacity (DLco) (r = –0.35 to –0.61, p < 0.05) and weak positive correlations with TLC (r = 0.34 to 0.44, p < 0.05). Group analysis indicated that LAV_{–950 HU} (%) values of both lungs, right lung, left lung, and each lobe, except for right middle lobe, were increased in patients with GOLD stages 3 and 4 of COPD compared to GOLD stages 1 and 2 (p < 0.05).

Conclusion.

CT measurements of emphysema are significantly related to pulmonary function tests results, particularly DLco.

Significance of Low-Attenuation Cluster Analysis on Quantitative CT in the Evaluation of Chronic Obstructive Pulmonary Disease

Objective

To assess clinical feasibility of low-attenuation cluster analysis in evaluation of chronic obstructive pulmonary disease (COPD).

Materials and Methods

Subjects were 199 current and former cigarette smokers that underwent CT for quantification of COPD and had physiological measurements. Quantitative CT (QCT) measurements included low-attenuation area percent (LAA%) (voxels ≤ -950 Hounsfield unit [HU]), and two-dimensional (2D) and three-dimensional D values of cluster analysis at three different thresholds of CT value (-856, -910, and -950 HU). Correlation coefficients between QCT measurements and physiological indices were calculated. Multivariable analyses for percentage of predicted forced expiratory volume at one second (%FEV1) was performed including sex, age, body mass index, LAA%, and D value had the highest correlation coefficient with %FEV1 as independent variables. These analyses were conducted in subjects including those with mild COPD (global initiative of chronic obstructive lung disease stage = 0-II).

Results

LAA% had a higher correlation coefficient (-0.549, p < 0.001) with %FEV1 than D values in subjects while 2D D_-910HU (-0.350, p < 0.001) revealed slightly higher correlation coefficient than LAA% (-0.343, p < 0.001) in subjects with mild COPD. Multivariable analyses revealed that LAA% and 2D D value_-910HU were significant independent predictors of %FEV1 in subjects and that only 2D D value_-910HU revealed a marginal p value (0.05) among independent variables in subjects with mild COPD.

Conclusion

Low-attenuation cluster analysis provides incremental information regarding physiologic severity of COPD, independent of LAA%, especially with mild COPD.

CT densitometry in emphysema: a systematic review of its clinical utility

BACKGROUND

The aim of the study was to assess the relationship between computed tomography (CT) densitometry and routine clinical markers in patients with chronic obstructive pulmonary disease (COPD) and alpha-1 anti-trypsin deficiency (AATD).

METHODS

Multiple databases were searched using a combination of pertinent terms and those articles relating quantitatively measured CT densitometry to clinical outcomes. Studies that used visual scoring only were excluded, as were those measured in expiration only. A thorough review of abstracts and full manuscripts was conducted by 2 reviewers; data extraction and assessment of bias was conducted by 1 reviewer and the 4 reviewers independently assessed for quality. Pooled correlation coefficients were calculated, and heterogeneity was explored.

RESULTS

A total of 112 studies were identified, 82 being suitable for meta-analysis. The most commonly used density threshold was -950 HU, and a significant association between CT density and all included clinical parameters was demonstrated. There was marked heterogeneity between studies secondary to large variety of disease severity within commonly included cohorts and differences in CT acquisition parameters.

CONCLUSION

CT density shows a good relationship to clinically relevant parameters; however, study heterogeneity and lack of longitudinal data mean that it is difficult to compare studies or derive a minimal clinically important difference. We recommend that international consensus is reached to standardize CT conduct and analysis in future COPD and AATD studies.

Visual Assessment of Chest Computed Tomographic Images Is Independently Useful for Genetic Association Analysis in Studies of Chronic Obstructive Pulmonary Disease

RATIONALE

Automated analysis of computed tomographic (CT) lung images for epidemiologic and genetic association studies is increasingly common, but little is known about the utility of visual versus semiautomated emphysema and airway assessments for genetic association studies.

OBJECTIVES

Assess the relative utility of visual versus semiautomated emphysema and airway assessments for genetic association studies.

METHODS

A standardized inspection protocol was used to visually assess chest CT images for 1,540 non-Hispanic white subjects within the COPDGene Study for the presence and severity of radiographic features representing airway wall thickness and emphysema. A genome-wide association study (GWAS) was performed, and two sets of candidate single-nucleotide polymorphisms with a higher prior likelihood of association were specified a priori for separate analysis. For each visual CT examination feature, a corresponding semiautomated CT feature(s) was identified for comparison in the same subjects.

MEASUREMENTS AND MAIN RESULTS

GWAS for visual features of chest CT scans identified a genome-wide significant association with visual emphysema at the 15q25 locus (P = 6.3e^-9). In the a priori-specified set of 19 previously identified GWAS loci, 7 and 8 loci were associated with airway measures or emphysema measures, respectively. In the a priori-specified candidate gene set, 13 of 196 candidate genes harbored a nearby single-nucleotide polymorphism significantly associated with an emphysema phenotype. Visual CT examination associations were robust to adjustment for semiautomated correlates in many cases.

CONCLUSIONS

Standardized visual assessments of emphysema and airway disease are significantly associated with genetic loci previously associated with chronic obstructive pulmonary disease susceptibility or semiautomated CT examination phenotypes in GWAS. Visual CT measures of emphysema and airways disease offer independent information for genetic association studies in relation to standard semiautomated measures.

A new functional method to choose the target lobe for lung volume reduction in emphysema - comparison with the conventional densitometric method

Background

Lung volume reduction (LVR) improves breathing mechanics by reducing hyperinflation. Lobar selection usually focuses on choosing the most destroyed emphysematous lobes as seen on an inspiratory CT scan. However, it has never been shown to what extent these densitometric CT parameters predict the least deflation of an individual lobe during expiration. The addition of expiratory CT analysis allows measurement of the extent of lobar air trapping and could therefore provide additional functional information for choice of potential treatment targets.

Objectives

To determine lobar vital capacity/lobar total capacity (LVC/LTC) as a functional parameter for lobar air trapping using on an inspiratory and expiratory CT scan. To compare lobar selection by LVC/LTC with the established morphological CT density parameters.

Methods

36 patients referred for endoscopic LVR were studied. LVC/LTC, defined as delta volume over maximum volume of a lobe, was calculated using inspiratory and expiratory CT scans. The CT morphological parameters of mean lung density (MLD), low attenuation volume (LAV), and 15th percentile of Hounsfield units (15%P) were determined on an inspiratory CT scan for each lobe. We compared and correlated LVC/LTC with MLD, LAV, and 15%P.

Results

There was a weak correlation between the functional parameter LVC/LTC and all inspiratory densitometric parameters. Target lobe selection using lowest lobar deflation (lowest LVC/LTC) correlated with target lobe selection based on lowest MLD in 18 patients (50.0%), with the highest LAV in 13 patients (36.1%), and with the lowest 15%P in 12 patients (33.3%).

Conclusion

CT-based measurement of deflation (LVC/LTC) as a functional parameter correlates weakly with all densitometric CT parameters on a lobar level. Therefore, morphological criteria based on inspiratory CT densitometry partially reflect the deflation of particular lung lobes, and may be of limited value as a sole predictor for target lobe selection in LVR.

Multivariate modeling using quantitative CT metrics may improve accuracy of diagnosis of bronchiolitis obliterans syndrome after lung transplantation

BACKGROUND

To assess how quantitative CT (qCT) metrics compare to pulmonary function testing (PFT) and semi-quantitative image scores (SQS) to diagnose bronchiolitis obliterans syndrome (BOS), manifestation of chronic lung allograft dysfunction after lung transplantation (LTx), according to the type of LTx (unilateral or bilateral).

METHODS

Paired inspiratory-expiratory CT scans and PFTs of 176 LTx patients were analyzed retrospectively, and separated into BOS (78) and non-BOS (98) cohorts. SQS were assessed by 2 radiologists and graded (0-3) for features including mosaic attenuation and bronchiectasis. qCT metrics included lung volumes and air trapping volumes. Multivariate logistic regression (MVLR) and support vector machines (SVM) were used for the classification task.

RESULTS

MVLR and SVM models using PFT metrics demonstrated highest accuracy for bilateral LTx (max AUC 0.771), whereas models using qCT metrics-only outperformed models using SQS or PFTs in unilateral LTx (max AUC 0.817), to diagnose BOS. Adding PC (principal components) from qCT on top of PFT improved model diagnostic accuracy for all transplant types.

CONCLUSIONS

Combinations of qCT metrics augment the diagnostic performance of PFTs, are superior to SQS to predict BOS status, and outperform PFTs in the unilateral LTx group. This suggests that latent information on paired volumetric CT may allow early diagnosis of BOS in LTx patients, particularly in unilateral LTx.

Low-dose cadmium exposure induces peribronchiolar fibrosis through site-specific phosphorylation of vimentin

Exposure to cadmium (Cd) has been associated with development of chronic obstructive lung disease (COPD). The mechanisms and signaling pathways whereby Cd causes pathological peribronchiolar fibrosis, airway remodeling, and subsequent airflow obstruction remain unclear. We aimed to evaluate whether low-dose Cd exposure induces vimentin phosphorylation and Yes-associated protein 1 (YAP1) activation leading to peribronchiolar fibrosis and subsequent airway remodeling. Our data demonstrate that Cd induces myofibroblast differentiation and extracellular matrix (ECM) deposition around small (<2 mm in diameter) airways. Upon Cd exposure, α-smooth muscle actin (α-SMA) expression and the production of ECM proteins, including fibronectin and collagen-1, are markedly induced in primary human lung fibroblasts. Cd induces Smad2/3 activation and the translocation of both Smad2/3 and Yes-associated protein 1 (YAP1) into the nucleus. In parallel, Cd induces AKT and cdc2 phosphorylation and downstream vimentin phosphorylation at Ser³⁹ and Ser⁵⁵, respectively. AKT and cdc2 inhibitors block Cd-induced vimentin fragmentation and secretion in association with inhibition of α-SMA expression, ECM deposition, and collagen secretion. Furthermore, vimentin silencing abrogates Cd-induced α-SMA expression and decreases ECM production. Vimentin-deficient mice are protected from Cd-induced peribronchiolar fibrosis and remodeling. These findings identify two specific sites on vimentin that are phosphorylated by Cd and highlight the functional significance of vimentin phosphorylation in YAP1/Smad3 signaling that mediates Cd-induced peribronchiolar fibrosis and airway remodeling.

CT-derived Biomechanical Metrics Improve Agreement Between Spirometry and Emphysema

RATIONALE AND OBJECTIVES

Many patients with chronic obstructive pulmonary disease (COPD) have marked discordance between forced expiratory volume in 1 second (FEV1) and degree of emphysema on computed tomography (CT). Biomechanical differences between these patients have not been studied. We aimed to identify reasons for the discordance between CT and spirometry in some patients with COPD.

MATERIALS AND METHODS

Subjects with Global initiative for chronic Obstructive Lung Disease stages I-IV from a large multicenter study (The Genetic Epidemiology of COPD) were arranged by percentiles of %predicted FEV1 and emphysema on CT. Three categories were created using differences in percentiles: Catspir with predominant airflow obstruction/minimal emphysema, CatCT with predominant emphysema/minimal airflow obstruction, and Catmatched with matched FEV1 and emphysema. Image registration was used to derive Jacobian determinants, a measure of lung elasticity, anisotropy, and strain tensors, to assess biomechanical differences between groups. Regression models were created with the previously mentioned categories as outcome variable, adjusting for demographics, scanner type, quantitative CT-derived emphysema, gas trapping, and airway thickness (model 1), and after adding biomechanical CT metrics (model 2).

RESULTS

Jacobian determinants, anisotropy, and strain tensors were strongly associated with FEV1. With Catmatched as control, model 2 predicted Catspir and CatCT better than model 1 (Akaike information criterion 255.8 vs. 320.8). In addition to demographics, the strongest independent predictors of FEV1 were Jacobian mean (β = 1.60,95%confidence intervals [CI] = 1.16 to 1.98; P < 0.001), coefficient of variation (CV) of Jacobian (β = 1.45,95%CI = 0.86 to 2.03; P < 0.001), and CV of strain (β = 1.82,95%CI = 0.68 to 2.95; P = 0.001). CVs of Jacobian and strain are both potential markers of biomechanical lung heterogeneity.

CONCLUSIONS

CT-derived measures of lung mechanics improve the link between quantitative CT and spirometry, offering the potential for new insights into the linkage between regional parenchymal destruction and global decrement in lung function in patients with COPD.

Imaging biomarkers in the clinic

Multimodality medical imaging offers a key role in disease diagnosis, while providing accurate staging and defining disease extent in many instances. Recent developments are increasingly leading to quantitative assessment of medical images, allowing both definition of disease extent, giving insight into the phenotypes of diseases and offering capabilities of monitoring response to therapy. Combined with other tools, such as genetic profiling, this is a powerful way of improving diagnosis and treatment of patients, enabling a personalized approach to delivering healthcare. It is highly likely that software tools will become integrated into the routine workflow of radiology reports. This special report describes some of the crucial areas where applications are being introduced and speculate on the potential impact on radiologists and clinicians.

Quantitative computed tomography measurements to evaluate airway disease in chronic obstructive pulmonary disease: Relationship to physiological measurements, clinical index and visual assessment of airway disease

PURPOSE

To correlate currently available quantitative CT measurements for airway disease with physiological indices and the body-mass index, airflow obstruction, dyspnea, and exercise capacity (BODE) index in patients with chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

This study was approved by our institutional review board (IRB number 2778). Written informed consent was obtained from all subjects. The subjects included 188 current and former cigarette smokers from the COPDGene cohort who underwent inspiratory and expiratory CT and also had physiological measurements for the evaluation of airflow limitation, including FEF25-75%, airway resistance (Raw), and specific airway conductance (sGaw). The BODE index was used as the index of clinical symptoms. Quantitative CT measures included % low attenuation areas [% voxels≤950 Hounsfield unit (HU) on inspiratory CT, %LAA_-950ins], percent gas trapping (% voxels≤-856HU on expiratory CT, %LAA _-856exp), relative inspiratory to expiratory volume change of voxels with attenuation values from -856 to -950HU [Relative Volume Change (RVC)_{-856 to -950}], expiratory to inspiratory ratio of mean lung density (E/I-ratio _MLD), Pi10, and airway wall thickness (WT), luminal diameter (LD) and airway wall area percent (WA%) in the segmental, subsegmental and subsubsegmental bronchi on inspiratory CT. Correlation coefficients were calculated between the QCT measurements and physiological measurements in all subjects and in the subjects with mild emphysema (%LAA_-950ins <10%). Univariate and multiple variable analysis for the BODE index were also performed. Adjustments were made for age, gender, smoking pack years, FEF25-75%, Raw, and sGaw.

RESULTS

Quantitative CT measurements had significant correlations with physiological indices. Among them, E/I-ratio _MLD had the strongest correlations with FEF25-75% (r=-0.648, <0.001) and sGaw (r=-0.624, <0.001) while in the subjects with mild emphysema subsegmental WA% and segmental WA% had the strongest correlation with FEF25-75% (r=-0.669, <0.001) and sGaw (r=-0.638, <0.001), respectively. The multiple variable analyses showed that RVC_{-856 to -950} was an independent predictor of the BODE index showing the highest R² (0.468) as an independent variable among the QCT measurements.

CONCLUSION

Quantitative CT measurements of gas trapping such as E/I-ratio _MLD, correlate better with physiological indices for airway disease than those of airway such as WA% or LD. In mild emphysema, however, quantitative CT measurements of airway correlate better with the physiological indices. RVC_{-856 to -950} is a predictor of the BODE index.

Pulmonary CT and MRI phenotypes that help explain chronic pulmonary obstruction disease pathophysiology and outcomes

Pulmonary x-ray computed tomographic (CT) and magnetic resonance imaging (MRI) research and development has been motivated, in part, by the quest to subphenotype common chronic lung diseases such as chronic obstructive pulmonary disease (COPD). For thoracic CT and MRI, the main COPD research tools, disease biomarkers are being validated that go beyond anatomy and structure to include pulmonary functional measurements such as regional ventilation, perfusion, and inflammation. In addition, there has also been a drive to improve spatial and contrast resolution while at the same time reducing or eliminating radiation exposure. Therefore, this review focuses on our evolving understanding of patient-relevant and clinically important COPD endpoints and how current and emerging MRI and CT tools and measurements may be exploited for their identification, quantification, and utilization. Since reviews of the imaging physics of pulmonary CT and MRI and reviews of other COPD imaging methods were previously published and well-summarized, we focus on the current clinical challenges in COPD and the potential of newly emerging MR and CT imaging measurements to address them. Here we summarize MRI and CT imaging methods and their clinical translation for generating reproducible and sensitive measurements of COPD related to pulmonary ventilation and perfusion as well as parenchyma morphology. The key clinical problems in COPD provide an important framework in which pulmonary imaging needs to rapidly move in order to address the staggering burden, costs, as well as the mortality and morbidity associated with COPD.

A Genome-Wide Association Study of Emphysema and Airway Quantitative Imaging Phenotypes

RATIONALE

Chronic obstructive pulmonary disease (COPD) is defined by the presence of airflow limitation on spirometry, yet subjects with COPD can have marked differences in computed tomography imaging. These differences may be driven by genetic factors. We hypothesized that a genome-wide association study (GWAS) of quantitative imaging would identify loci not previously identified in analyses of COPD or spirometry. In addition, we sought to determine whether previously described genome-wide significant COPD and spirometric loci were associated with emphysema or airway phenotypes.

OBJECTIVES

To identify genetic determinants of quantitative imaging phenotypes.

METHODS

We performed a GWAS on two quantitative emphysema and two quantitative airway imaging phenotypes in the COPDGene (non-Hispanic white and African American), ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints), NETT (National Emphysema Treatment Trial), and GenKOLS (Genetics of COPD, Norway) studies and on percentage gas trapping in COPDGene. We also examined specific loci reported as genome-wide significant for spirometric phenotypes related to airflow limitation or COPD.

MEASUREMENTS AND MAIN RESULTS

The total sample size across all cohorts was 12,031, of whom 9,338 were from COPDGene. We identified five loci associated with emphysema-related phenotypes, one with airway-related phenotypes, and two with gas trapping. These loci included previously reported associations, including the HHIP, 15q25, and AGER loci, as well as novel associations near SERPINA10 and DLC1. All previously reported COPD and a significant number of spirometric GWAS loci were at least nominally (P < 0.05) associated with either emphysema or airway phenotypes.

CONCLUSIONS

Genome-wide analysis may identify novel risk factors for quantitative imaging characteristics in COPD and also identify imaging features associated with previously identified lung function loci.

Correlation Between Emphysema and Lung Function in Healthy Smokers and Smokers With COPD

Background: Emphysema is an important component of COPD; however, in previous studies of the correlation between airflow limitation (AFL) and computed tomography (CT) lung density as a surrogate for emphysema has varied. We hypothesised a good correlation between lung function (forced expiratory volume in first second [FEV₁]) and emphysema (15^th percentile density [PD15]) and that this correlation also exists between loss of lung tissue and decline in lung function even within the time frame of longitudinal studies of relatively short duration. Methods: We combined 2 large longitudinal studies (the Danish Lung Cancer Screening Trial [DLCST] and the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints [ECLIPSE]) of smokers or former smokers, with a wide range of AFL and CT lung density, and analysed data from 2148 participants who did not change smoking habits and who had at least 2 CT scans and 2 FEV₁ measurements at least 3 years apart. Results: Baseline correlation between FEV₁ and PD15 was high (r=0.716, 95% confidence interval [CI]: 0.694-0.736, p<0.001) indicating that at least half of the variation in FEV₁ can be explained by variation in CT lung density. Correlation between the decline in FEV₁ and progression of PD15 was considerably weaker (r= 0.081, 95% CI: 0.038-0.122, p<0.001). Conclusions: Correlation is very high between lung density and lung function in a broad spectrum of smokers and ex-smokers. In contrast, the temporal associations (slopes) are weakly correlated, probably due to uncertainty in the estimation of slopes within a time frame of 3-4 years.

Quantitative emphysema assessment of pulmonary function impairment by computed tomography in chronic obstructive pulmonary disease

OBJECTIVE

The objective of this study was to determine the capability of quantitative emphysema by computed tomography (CT) to assess pulmonary function impairment in a population of current smokers with and without airflow limitation.

METHODS

Seventy-six subjects (30 normal smokers; 8 with mild obstruction; 17 with moderate obstruction; 13 with severe obstruction; 8 with very severe obstruction) underwent CT examinations and pulmonary function tests. For the quantitative assessment, percentages of low attenuation volume (%LAVs) of whole lung, right lung, left lung, and each lobe were obtained. Computed tomography measurements were related to lung function (forced expiratory volume in 1 second [FEV1], ratio of FEV1 to forced vital capacity, diffusing capacity for carbon monoxide [DLCO], ratio of residual volume to total lung capacity [RV/TLC]) by multivariate linear regression analysis.

RESULTS

Quantitative CT measurements of emphysema were moderately, negatively correlated to airflow limitation (FEV1 and ratio of FEV1 to forced vital capacity) (r = -0.68 to -0.52, P < 0.001). Except for right middle and lower lobes, all the quantitative CT measurements showed moderate, negative correlations with diffusing capacity (DLCO) (r = -0.63 to -0.54, P ≤ 0.001) and weak to moderate correlations with RV (RV/TLC) (r = 0.36-0.41, P < 0.01). As compared with control samples, the %LAV of whole lung, right lung, left lung, and each lobe was increased in patients with GOLD stages 2, 3, and 4 disease (P < 0.05), and the % LAV of whole lung, right lung and right upper lobe was increased in patients with GOLD stage 1 (P < 0.05).

CONCLUSIONS

Pulmonary function results, particularly DLCO and RV/TLC, were primarily affected by the % LAV of the upper lobes. Quantitative CT measurements of emphysema provides a morphological method to investigate lung function impairment in patients with chronic obstructive pulmonary disease.

Variation in the percent of emphysema-like lung in a healthy, nonsmoking multiethnic sample. The MESA lung study

RATIONALE

Computed tomography (CT)-based lung density is used to quantitate the percentage of emphysema-like lung (hereafter referred to as percent emphysema), but information on its distribution among healthy nonsmokers is limited.

OBJECTIVES

We evaluated percent emphysema and total lung volume on CT scans of healthy never-smokers in a multiethnic, population-based study.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) Lung Study investigators acquired full-lung CT scans of 3,137 participants (ages 54-93 yr) between 2010-12. The CT scans were taken at full inspiration following the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) protocol. "Healthy never-smokers" were defined as participants without a history of tobacco smoking or respiratory symptoms and disease. "Percent emphysema" was defined as the percentage of lung voxels below -950 Hounsfield units. "Total lung volume" was defined by the volume of lung voxels.

MEASUREMENTS AND MAIN RESULTS

Among 854 healthy never-smokers, the median percent emphysema visualized on full-lung scans was 1.1% (interquartile range, 0.5-2.5%). The percent emphysema values were 1.2 percentage points higher among men compared with women and 0.7, 1.2, and 1.2 percentage points lower among African Americans, Hispanics, and Asians compared with whites, respectively (P < 0.001). Percent emphysema was positively related to age and height and inversely related to body mass index. The findings were similar for total lung volume on CT scans and for percent emphysema defined at -910 Hounsfield units and measured on cardiac scans. Reference equations to account for these differences are presented for never, former and current smokers.

CONCLUSIONS

Similar to lung function, percent emphysema varies substantially by demographic factors and body size among healthy never-smokers. The presented reference equations will assist in defining abnormal values for percent emphysema and total lung volume on CT scans, although validation is pending.

Chronic obstructive pulmonary disease: NHLBI Workshop on the Primary Prevention of Chronic Lung Diseases

Chronic obstructive pulmonary disease (COPD) is a complex set of conditions with multiple risk factors, disease mechanisms, and clinical manifestations. These characteristics make primary prevention of COPD challenging. Semantic issues related to prevalent and incident disease (e.g., the use of specific cut points on a continuous range) should not derail development of primary prevention initiatives. Potential targets for COPD prevention occur along the spectrum of disease development. Understanding risk factors early in life, whether specific to COPD or not, allows for study of interventions to optimize lung function at birth and to prolong the lung function plateau, potentially reducing the development of COPD. It is necessary to identify noninvasive ways to screen for early COPD in those at risk before progression to clinically significant disease. Identification of specific COPD subgroups, such as individuals with chronic bronchitis, those with α1-antitrypsin deficiency, or early radiographic changes with normal spirometry, may offer specific opportunities for primary prevention. A better understanding of why COPD progresses despite smoking cessation is needed. Future research initiatives should also focus on identifying the underlying mechanisms and relevant interventions for nonsmokers with COPD, a currently poorly studied group. Ultimately, preventing the development of COPD will serve to reduce the tremendous burden of this chronic disease worldwide.

Delay of airway epithelial wound repair in COPD is associated with airflow obstruction severity

BACKGROUND

Airway epithelium integrity is essential to maintain its role of mechanical and functional barrier. Recurrent epithelial injuries require a complex mechanism of repair to restore its integrity. In chronic obstructive pulmonary disease (COPD), an abnormal airway epithelial repair may participate in airway remodeling. The objective was to determine if airway epithelial wound repair of airway epithelium is abnormal in COPD.

METHODS

Patients scheduled for lung resection were prospectively recruited. Demographic, clinical data and pulmonary function tests results were recorded. Emphysema was visually scored and histological remodeling features were noted. Primary bronchial epithelial cells (BEC) were extracted and cultured for wound closure assay. We determined the mean speed of wound closure (MSWC) and cell proliferation index, matrix metalloprotease (MMP)-2, MMP-9 and cytokines levels in supernatants of BEC 18 hours after cell wounding. In a subset of patients, bronchiolar epithelial cells were also cultured for wound closure assay for MSWC analyze.

RESULTS

13 COPD and 7 non COPD patients were included. The severity of airflow obstruction and the severity of emphysema were associated with a lower MSWC in BEC (p = 0.01, 95% CI [0.15-0.80]; p = 0.04, 95% CI [-0.77;-0.03] respectively). Cell proliferation index was decreased in COPD patients (19 ± 6% in COPD vs 27 ± 3% in non COPD, p = 0.04). The severity of COPD was associated with a lower level of MMP-2 (7.8 ± 2 10(5) AU in COPD GOLD D vs 12.8 ± 0.13 10(5) AU in COPD GOLD A, p = 0.04) and a lower level of IL-4 (p = 0.03, 95% CI [0.09;0.87]). Moreover, higher levels of IL-4 and IL-2 were associated with a higher MSWC (p = 0.01, 95% CI [0.17;0.89] and p = 0.02, 95% CI [0.09;0.87] respectively). Clinical characteristics and smoking history were not associated with MSWC, cell proliferation index or MMP and cytokines levels. Finally, we showed an association of the MSWC of bronchial and corresponding bronchiolar epithelial cells obtained from the same patients (p = 0.02, 95% CI [0.12;0.89]).

CONCLUSION

Our results showed an abnormal bronchial epithelial wound closure process in severe COPD. Further studies are needed to elucidate the contribution and the regulation of this mechanism in the complex pathophysiology of COPD.

Autoreactivity to glucose regulated protein 78 links emphysema and osteoporosis in smokers

Rationale

Emphysema and osteoporosis are epidemiologically associated diseases of cigarette smokers. The causal mechanism(s) linking these illnesses is unknown. We hypothesized autoimmune responses may be involved in both disorders.

Objectives

To discover an antigen-specific autoimmune response associated with both emphysema and osteoporosis among smokers.

Methods

Replicate nonbiased discovery assays indicated that autoimmunity to glucose regulated protein 78 (GRP78), an endoplasmic reticulum chaperone and cell surface signaling receptor, is present in many smokers. Subject assessments included spirometry, chest CT scans, dual x-ray absorptiometry, and immunoblots for anti-GRP78 IgG. Anti-GRP78 autoantibodies were isolated from patient plasma by affinity chromatography, leukocyte functions assessed by flow cytometry, and soluble metabolites and mediators measured by immunoassays.

Measurements and Main Results

Circulating anti-GRP78 IgG autoantibodies were detected in plasma specimens from 86 (32%) of the 265 smoking subjects. Anti-GRP78 autoantibodies were singularly prevalent among subjects with radiographic emphysema (OR 3.1, 95%CI 1.7–5.7, p = 0.003). Anti-GRP78 autoantibodies were also associated with osteoporosis (OR 4.7, 95%CI 1.7–13.3, p = 0.002), and increased circulating bone metabolites (p = 0.006). Among emphysematous subjects, GRP78 protein was an autoantigen of CD4 T-cells, stimulating lymphocyte proliferation (p = 0.0002) and IFN-gamma production (p = 0.03). Patient-derived anti-GRP78 autoantibodies had avidities for osteoclasts and macrophages, and increased macrophage NFkB phosphorylation (p = 0.005) and productions of IL-8, CCL-2, and MMP9 (p = 0.005, 0.007, 0.03, respectively).

Conclusions

Humoral and cellular GRP78 autoimmune responses in smokers have numerous biologically-relevant pro-inflammatory and other deleterious actions, and are associated with emphysema and osteoporosis. These findings may have relevance for the pathogenesis of smoking-associated diseases, and development of biomarker immunoassays and/or novel treatments for these disorders.

COPD phenotypes in a lung cancer screening population

BACKGROUND AND AIMS

COPD (chronic obstructive pulmonary disease) is a very heterogeneous disease, and phenotypic categorization of a high-risk population has many potential benefits. The present study uses a symptom questionnaire, low-dose computed tomography (LDCT) and pulmonary function tests (PFT) to phenotypically subgroup a high-risk population.

METHODS

Study group consisted of current or former smokers who underwent lung cancer screening with LDCT as a subgroup of Pittsburgh Lung Screening Study. In addition to LDCT, PFT and a symptom query questionnaire were obtained from each patient.

RESULTS

The study group consisted of 3183 subjects (age 50-79) subdivided into eight groups according to presence of symptoms, obstruction on PFT and presence of emphysema on LDCT. A total of 501 (15.7%) subjects were asymptomatic, with no airflow obstruction or evidence of emphysema. There were 866 (27.2%) subjects with both obstruction on PFT and emphysema on LDCT, but only 660 (20.7%) had symptoms. Five hundred thirty (16.6%) of the subjects had no emphysema on LDCT but had obstruction on PFT, although only 370 (11.6%) had symptoms. Four hundred seventy-four (14.9%) of subjects had emphysema on LDCT, but no airflow obstruction, with 312 (9.8%) symptomatic. Finally, 812 (25.5%) of subjects had no evidence of airflow obstruction on PFT or emphysema on LDCT, but had symptoms.

CONCLUSION

Combining LDCT with PFT and a comprehensive questionnaire allows subgroup classification of COPD phenotypes in a high-risk population and may lead to earlier intervention and an improved framework for future studies.

Disproportionate contribution of right middle lobe to emphysema and gas trapping on computed tomography

RATIONALE

Given that the diagnosis of chronic obstructive pulmonary disease (COPD) relies on demonstrating airflow limitation by spirometry, which is known to be poorly sensitive to early disease, and to regional differences in emphysema, we sought to evaluate individual lobar contributions to global spirometric measures.

METHODS

Subjects with COPD were compared with smokers without airflow obstruction, and non-smokers. Emphysema (% low attenuation area, LAAinsp<-950 HU, at end-inspiration) and gas trapping (%LAAexp<-856 HU at end-expiration) on CT were quantified using density mask analyses for the whole lung and for individual lobes, and distribution across lobes and strength of correlation with spirometry were compared.

RESULTS

The right middle lobe had the highest %LAAinsp<-950 HU in smokers and controls, and the highest %LAAexp<-856 HU in all three groups. While RML contributed to emphysema and gas trapping disproportionately to its relatively small size, it also showed the least correlation with spirometry. There was no change in correlation of whole lung CT metrics with spirometry when the middle lobe was excluded from analyses. Similarly, RML had the highest %LAAexp<-856 HU while having the least correlation with spirometry.

CONCLUSIONS

Because of the right middle lobe's disproportionate contribution to CT-based emphysema measurements, and low contribution to spirometry, longitudinal studies of emphysema progression may benefit from independent analysis of the middle lobe in whole lung quantitative CT assessments. Our findings may also have implications for heterogeneity assessments and target lobe selection for lung volume reduction.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT00608764.

Direct assessment of lung function in COPD using CT densitometric measures

To investigate whether lung function in patients with chronic obstructive pulmonary disease (COPD) can be directly predicted using CT densitometric measures and assess the underlying prediction errors as compared with the traditional spirometry-based measures. A total of 600 CT examinations were collected from a COPD study. In addition to the entire lung volume, the extent of emphysema depicted in each CT examination was quantified using density mask analysis (densitometry). The partial least square regression was used for constructing the prediction model, where a repeated random split-sample validation was employed. For each split, we randomly selected 400 CT exams for training (regression) purpose and the remaining 200 exams for assessing performance in prediction of lung function (e.g., FEV1 and FEV1/FVC) and disease severity. The absolute and percentage errors as well as their standard deviations were computed. The averaged percentage errors in prediction of FEV1, FEV1/FVC%, TLC, RV/TLC% and DLco% predicted were 33%, 17%, 9%, 18% and 23%, respectively. When classifying the exams in terms of disease severity grades using the CT measures, 37% of the subjects were correctly classified with no error and 83% of the exams were either correctly classified or classified into immediate neighboring categories. The linear weighted kappa and quadratic weighted kappa were 0.54 (moderate agreement) and 0.72 (substantial agreement), respectively. Despite the existence of certain prediction errors in quantitative assessment of lung function, the CT densitometric measures could be used to relatively reliably classify disease severity grade of COPD patients in terms of GOLD.

Risk loci for chronic obstructive pulmonary disease: a genome-wide association study and meta-analysis

BACKGROUND

The genetic risk factors for susceptibility to chronic obstructive pulmonary disease (COPD) are still largely unknown. Additional genetic variants are likely to be identified by genome-wide association studies in larger cohorts or specific subgroups. We sought to identify risk loci for moderate to severe and severe COPD with data from several cohort studies.

METHODS

We combined genome-wide association analysis data from participants in the COPDGene study (non-Hispanic white and African-American ethnic origin) and the ECLIPSE, NETT/NAS, and Norway GenKOLS studies (self-described white ethnic origin). We did analyses comparing control individuals with individuals with moderate to severe COPD and with a subset of individuals with severe COPD. Single nucleotide polymorphisms yielding a p value of less than 5 × 10(-7) in the meta-analysis at loci not previously described were genotyped in individuals from the family-based ICGN study. We combined results in a joint meta-analysis (threshold for significance p<5 × 10(-8)).

FINDINGS

Analysis of 6633 individuals with moderate to severe COPD and 5704 control individuals confirmed association at three known loci: CHRNA3 (p=6·38 × 10(-14)), FAM13A (p=1·12 × 10(-14)), and HHIP (p=1·57 × 10(-12)). We also showed significant evidence of association at a novel locus near RIN3 (p=5·25 × 10(-9)). In the overall meta-analysis (ie, including data from 2859 ICGN participants), the association with RIN3 remained significant (p=5·4 × 10(-9)). 3497 individuals were included in our analysis of severe COPD. The effect estimates for the loci near HHIP and CHRNA3 were significantly stronger in severe disease than in moderate to severe disease (p<0·01). We also identified associations at two additional loci: MMP12 (overall joint meta-analysis p=2·6 × 10(-9)) and TGFB2 (overall joint meta-analysis p=8·3 × 10(-9)).

INTERPRETATION

We have confirmed associations with COPD at three known loci and identified three new genome-wide significant associations. Genetic variants other than in α-1 antitrypsin increase the risk of COPD.

FUNDING

US National Heart, Lung, and Blood Institute; the Alpha-1 Foundation; the COPD Foundation through contributions from AstraZeneca, Boehringer Ingelheim, Novartis, and Sepracor; GlaxoSmithKline; Centers for Medicare and Medicaid Services; Agency for Healthcare Research and Quality; and US Department of Veterans Affairs.

Distinct quantitative computed tomography emphysema patterns are associated with physiology and function in smokers

RATIONALE

Emphysema occurs in distinct pathologic patterns, but little is known about the epidemiologic associations of these patterns. Standard quantitative measures of emphysema from computed tomography (CT) do not distinguish between distinct patterns of parenchymal destruction.

OBJECTIVES

To study the epidemiologic associations of distinct emphysema patterns with measures of lung-related physiology, function, and health care use in smokers.

METHODS

Using a local histogram-based assessment of lung density, we quantified distinct patterns of low attenuation in 9,313 smokers in the COPDGene Study. To determine if such patterns provide novel insights into chronic obstructive pulmonary disease epidemiology, we tested for their association with measures of physiology, function, and health care use.

MEASUREMENTS AND MAIN RESULTS

Compared with percentage of low-attenuation area less than -950 Hounsfield units (%LAA-950), local histogram-based measures of distinct CT low-attenuation patterns are more predictive of measures of lung function, dyspnea, quality of life, and health care use. These patterns are strongly associated with a wide array of measures of respiratory physiology and function, and most of these associations remain highly significant (P < 0.005) after adjusting for %LAA-950. In smokers without evidence of chronic obstructive pulmonary disease, the mild centrilobular disease pattern is associated with lower FEV1 and worse functional status (P < 0.005).

CONCLUSIONS

Measures of distinct CT emphysema patterns provide novel information about the relationship between emphysema and key measures of physiology, physical function, and health care use. Measures of mild emphysema in smokers with preserved lung function can be extracted from CT scans and are significantly associated with functional measures.

Quantifying heterogeneity in emphysema from high-resolution computed tomography: a lung tissue research consortium study

RATIONALE AND OBJECTIVES

To quantify spatial distribution of emphysema using high-resolution computed tomography (HRCT), we applied semiautomated analysis with internal attenuation calibration to measure regional air volume, tissue volume, and fractional tissue volume (FTV = tissue/[air + tissue] volume) in well-characterized patients studied by the Lung Tissue Research Consortium (LTRC).

METHODS

HRCT was obtained at supine end-inspiration and end-expiration, and prone end-inspiration from 31 patients with mild, moderate, severe, or very severe emphysema (stages II-V, forced expiratory volume at 1 second >75%, 51%-75%, 21%-50% and ≤20% predicted, respectively). Control data were from 20 healthy non-smokers (stage I). Each lobe was analyzed separately. Heterogeneity of FTV was assessed from coefficients of variation (CV) within and among lobes, and the kurtosis and skewness of FTV histograms.

RESULTS

In emphysema, lobar air volume increased up to 177% above normal except in the right middle lobe. Lobar tissue volume increased up to 107% in mild-moderate stages then normalized in advanced stages. Normally, FTV was up to 82% higher in lower than upper lobes. In mild-moderate emphysema, lobar FTV increased by up to 74% above normal at supine inspiration. In severe emphysema, FTV declined below normal in all lobes and positions in correlation with pulmonary function (P < .05). Markers of FTV heterogeneity increased steadily with disease stage in correlation with pulmonary function (P < .05); the pattern is distinct from that seen in interstitial lung disease (ILD).

CONCLUSION

CT-derived biomarkers differentiate the spatial patterns of emphysema distribution and heterogeneity from that in ILD. Early emphysema is associated with elevated tissue volume and FTV, consistent with hyperemia, inflammation or atelectasis.

A comparative study of HRCT image metrics and PFT values for characterization of ILD and COPD

RATIONALE AND OBJECTIVES

The aim of this study was to compare the performance of various image-based metrics computed from thoracic high-resolution computed tomography (HRCT) with data from pulmonary function testing (PFT) in characterizing interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

Fourteen patients with ILD and 11 with COPD had undergone both PFT and HRCT within 3 days. For each patient, 93 image-based metrics were computed, and their relationships with the 21 clinically used PFT parameters were analyzed using a minimal-redundancy-maximal-relevance statistical framework. The first 20 features were selected among the total of 114 mixed image metrics and PFT values in the characterization of ILD and COPD.

RESULTS

Among the best-performing 20 features, 14 were image metrics, derived from attenuation histograms and texture descriptions. The highest relevance value computed from PFT parameters was 0.47, and the highest from image metrics was 0.52, given the theoretical bound as [0, 0.69]. The ILD or COPD classifier using the first four features achieved a 1.92% error rate.

CONCLUSIONS

Some image metrics are not only as good discriminators as PFT for the characterization of ILD and COPD but are also not redundant when PFT values are provided. Image metrics of attenuation histogram statistics and texture descriptions may be valuable for further investigation in computer-assisted diagnosis.

The role and potential of imaging in COPD

Chronic obstructive pulmonary disease is a heterogeneous condition of the lungs and body. Techniques in chest imaging and quantitative image analysis provide novel in vivo insight into the disease and potentially examine divergent responses to therapy. This article reviews the strengths and limitations of the leading imaging techniques: computed tomography, magnetic resonance imaging, positron emission tomography, and optical coherence tomography. Following an explanation of the technique, each section details some of the useful information obtained with these examinations. Future clinical care and investigation will likely include some combination of these imaging modalities and more standard assessments of disease severity.

Morphological measurements in computed tomography correlate with airflow obstruction in chronic obstructive pulmonary disease: systematic review and meta-analysis

Objectives

To determine the correlation between CT measurements of emphysema or peripheral airways and airflow obstruction in chronic obstructive pulmonary disease (COPD).

Methods

PubMed, Embase and Web of Knowledge were searched from 1976 to 2011. Two reviewers independently screened 1,763 citations to identify articles that correlated CT measurements to airflow obstruction parameters of the pulmonary function test in COPD patients, rated study quality and extracted information. Three CT measurements were accessed: lung attenuation area percentage < -950 Hounsfield units, mean lung density and airway wall area percentage. Two airflow obstruction parameters were accessed: forced expiratory volume in the first second as percentage from predicted (FEV₁ %pred) and FEV₁ divided by the forced volume vital capacity.

Results

Seventy-nine articles (9,559 participants) were included in the systematic review, demonstrating different methodologies, measurements and CT airflow obstruction correlations. There were 15 high-quality articles (2,095 participants) in the meta-analysis. The absolute pooled correlation coefficients ranged from 0.48 (95 % CI, 0.40 to 0.54) to 0.65 (0.58 to 0.71) for inspiratory CT and 0.64 (0.53 to 0.72) to 0.73 (0.63 to 0.80) for expiratory CT.

Conclusions

CT measurements of emphysema or peripheral airways are significantly related to airflow obstruction in COPD patients. CT provides a morphological method to investigate airway obstruction in COPD.

Key Points

• Computed tomography is widely performed in patients with chronic obstructive pulmonary disease (COPD)

• CT provides quantitative morphological methods to investigate airflow obstruction in COPD

• CT measurements correlate significantly with the degree of airflow obstruction in COPD

• Expiratory CT measurements correlate more strongly with airflow obstruction than inspiratory CT

• Low-dose CT decreases the radiation dose for diagnosis and quantitative emphysema evaluation

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-012-2480-8) contains supplementary material, which is available to authorized users.

The National Emphysema Treatment Trial (NETT): Part I: Lessons learned about emphysema

The National Emphysema Treatment Trial (NETT) was a multicenter prospective randomized controlled trial that compared optimal medical treatment, including pulmonary rehabilitation, with optimal medical treatment plus lung volume reduction surgery (LVRS). It was the largest and most complete collection of patient demographic, clinical, physiological, and radiographic data ever compiled in severe emphysema. NETT investigated the effects of optimal medical management and LVRS on short- and long-term survival, as well as lung function, exercise performance, and quality of life. NETT also provided much information regarding the evaluation and prognosis of severe emphysema; specifically the important negative influences that hyperinflation and small airway disease have on survival. NETT emphasized the importance of addressing nonpulmonary issues such as nutrition, cardiac disease, anxiety, and depression in emphysema. NETT demonstrated that physiological, genomic, and radiographic phenotype can predict patient survival as well as response to treatment. Because the major purpose of NETT was to compare bilateral LVRS with optimal medical treatment in emphysema, patients enrolled into NETT were comprehensively characterized and selected to have a specific window of airflow obstruction and hyperinflation and to lack significant comorbidities. The NETT patient population’s restrictive features offer distinct advantages (well-characterized predominant emphysematous phenotype) and disadvantages (lack of comorbidities and significant chronic bronchitis) that must be considered when interpreting the implications of these results. Herein, we provide a summary of the major NETT findings that provide insight into the evaluation and medical treatment of emphysema.

Polymorphisms in the superoxide dismutase-3 gene are associated with emphysema in COPD

Superoxide dismutase-3 (SOD3) is a major extracellular antioxidant enzyme, and previous studies have indicated a possible role of this gene in chronic obstructive pulmonary disease (COPD). We hypothesized that polymorphisms in the SOD3 gene would be associated with COPD and COPD-related phenotypes. We genotyped three SOD3 polymorphisms (rs8192287 (E1), rs8192288 (I1), and rs1799895 (R213G)) in a case-control cohort, with severe COPD cases from the National Emphysema Treatment Trial (NETT, n = 389) and smoking controls from the Normative Aging Study (NAS, n = 472). We examined whether the single nucleotide polymorphisms (SNPs) were associated with COPD status, lung function variables, and quantitative computed tomography (CT) measurements of emphysema and airway wall thickness. Furthermore, we tried to replicate our initial findings in two family-based studies, the International COPD Genetics Network (ICGN, n = 3061) and the Boston Early-Onset COPD Study (EOCOPD, n = 949). In NETT COPD cases, the minor alleles of SNPs E1 and I1 were associated with a higher percentage of emphysema (%LAA950) on chest CT scan (p = .029 and p = .0058). The association with E1 was replicated in the ICGN family study, where the minor allele was associated with more emphysema (p = .048). Airway wall thickness was positively associated with the E1 SNP in ICGN; however, this finding was not confirmed in NETT. Quantitative CT data were not available in EOCOPD. The SNPs were not associated with lung function variables or COPD status in any of the populations. In conclusion, polymorphisms in the SOD3 gene were associated with CT emphysema but not COPD susceptibility, highlighting the importance of phenotype definition in COPD genetics studies.

Quantitative CT measures of emphysema and airway wall thickness are related to D(L)CO

There is limited knowledge on the relationship between diffusing capacity of the lung for carbon monoxide (D(L)CO) and quantitative computed tomography (CT) measures of emphysema and airway wall thickness.

STUDY QUESTION

What is the relationship between D(L)CO and the quantitative CT measures of emphysema and airway wall thickness in subjects with and without COPD?

METHODS

We included 288 COPD subjects (70% men) and 425 non-COPD subjects (54% men). All subjects were current or ex-smokers older than 40 years and all subjects underwent spirometry, diffusing capacity tests and CT examination. Quantitative CT measures included % low attenuation areas < -950 HU (%LAA) and standardized airway wall thickness (AWT-Pi10).

RESULTS

Multiple linear regression analyses showed significant associations between D(L)CO and both %LAA and AWT-Pi10 in the COPD group. The adjusted regression coefficients (SE) for D(L)CO (mmol min(-1) kPa(-1)) were -1.15 (0.11) per 10% increase in %LAA and 0.08 (0.03) per 0.1 mm increase in AWT-Pi10, and the models' adjusted R(2) was 0.65 and 0.49, respectively.

CONCLUSIONS

CT measured emphysema explains a large fraction of the variation of D(L)CO among COPD subjects, and more so in men. Airway wall thickness is also significantly associated with D(L)CO, but explains a much smaller fraction of the variation.