High-resolution computed tomography scanning in alpha1-antitrypsin deficiency: relationship to lung function and health status

A Preliminary Study on the Relationship Between High-Resolution Computed Tomography and Pulmonary Function in People at Risk of Developing Chronic Obstructive Pulmonary Disease

Objectives

Patients with chronic obstructive pulmonary disease (COPD) have high morbidity and mortality, the opportunity to carry out a thoracic high-resolution CT (HRCT) scan may increase the possibility to identify the group at risk of disease. The aim of our study was to explore the differences in HRCT emphysema parameters, air trapping parameters, and lung density parameters between high and low-risk patients of COPD and evaluate their correlation with pulmonary function parameters.

Methods

In this retrospective, single-center cohort study, we enrolled outpatients from the Physical Examination Center and Respiratory Medicine of The First Affiliated Hospital of Wenzhou Medical University. The patients who were ≥ 40 years-old, had chronic cough or sputum production, and/or had exposure to risk factors for the disease and had not reached the diagnostic criteria is considered people at risk of COPD. They were divided into low-risk group and high-risk group according to FEV₁/FVC ≥ 80% and 80%>FEV₁/FVC ≥ 70%. Data on clinical characteristics, clinical symptom score, pulmonary function, and HRCT were recorded.

Results

72 COPD high-risk patients and 86 COPD low-risk patients were enrolled in the study, and the air trapping index of left, right, and bilateral lungs of the high-risk group were higher than those of the low-risk group. However, the result of mean expiratory lung density was opposite. The emphysema index of left, right, and bilateral lungs were negatively correlated with FEV₁/FVC (correlation coefficients were -0.33, -0.22, -0.26). Consistently, the air trapping index of left and right lungs and bilateral lungs were negatively correlated with FEV₁/FVC (correlation coefficients were -0.33, -0.23, -0.28). Additionally, the mean expiratory lung density of left and right lungs and bilateral lungs were positively correlated with FEV₁/FVC (correlation coefficients were 0.31, 0.25, 0.29).

Conclusion

The emphysema index, air trapping index and the mean expiratory lung density shows significantly positive correlation with FEV₁/FVC which can be used to assess the pulmonary function status of people at risk of COPD and provide a useful supplement for the early and comprehensive assessment of the disease.

Imaging in alpha-1 antitrypsin deficiency: a window into the disease

Imaging modalities such as plain chest radiograph and computed tomography (CT) are important tools in the assessment of patients with chronic obstructive pulmonary disease (COPD) of any etiology. These methods facilitate differential diagnoses and the assessment of individual lung pathologies, such as the presence of emphysema, bullae, or fibrosis. However, as emphysema is the core pathological consequence in the lungs of patients with alpha-1 antitrypsin deficiency (AATD), and because AATD is associated with the development of other lung pathologies such as bronchiectasis, there is a greater need for patients with AATD than those with non-AATD-related COPD to undergo more detailed assessment using CT. In the field of AATD, CT provides essential information regarding the presence, distribution, and morphology of emphysema. In addition, it offers the option to quantify the extent of emphysema. These data have implications for treatment decisions such as initiation of alpha-1 antitrypsin (AAT) therapy, or suitability for surgical or endoscopic interventions for reducing lung volume. Furthermore, CT has provided vital insight regarding the natural history of emphysema progression in AATD, and CT densitometry has underpinned research into the efficacy of AAT therapy. Moving forward, hyperpolarized xenon gas (129Xe) lung magnetic resonance imaging (MRI) is emerging as a promising complement to CT by adding comprehensive measures of regional lung function. It also avoids the main disadvantage of CT: the associated radiation. This chapter provides an overview of technological aspects of imaging in AATD, as well as its role in the management of patients and clinical research. In addition, perspectives on the future potential role of lung MRI in AATD are outlined.

The Emerging Role of Quantification of Imaging for Assessing the Severity and Disease Activity of Emphysema, Airway Disease, and Interstitial Lung Disease

There has been an explosion of use for quantitative image analysis in the setting of lung disease due to advances in acquisition protocols and postprocessing technology, including machine and deep learning. Despite the plethora of published papers, it is important to understand which approach has clinical validation and can be used in clinical practice. This paper provides an introduction to quantitative image analysis techniques being used in the investigation of lung disease and focusses on the techniques that have a reasonable clinical validation for being used in clinical trials and patient care.

Relationship of CT densitometry to lung physiological parameters and health status in alpha-1 antitrypsin deficiency: initial report of a centralised database of the NIHR rare diseases translational research collaborative

OBJECTIVES

To establish a database network for the study of alpha-1 antitrypsin deficiency (AATD) and compare the results to CT lung density as the most direct measure of emphysema.

DESIGN

A central electronic database was established to permit the upload of anonymised patient data from remote sites. Prospectively collected CT data were recorded onto disc, anonymised, analysed at the coordinating centre and compared with the clinical features of the disease.

SETTING

Tertiary referral centres with expertise in the management of AATD focused on academic Biomedical Research Units and Wellcome Clinical Research Facilities.

PARTICIPANTS

Data were collected from 187 patients over 1 year from eight UK academic sites. This included patient demographics, postbronchodilator physiology, health status and CT. Analysis was undertaken at the coordinating centre in Birmingham.

RESULTS

Patient recruitment in the 12 months reached 94% of target (set at 200) covering the whole spectrum of the disease from those with normal lung function to very severe chronic obstructive lung disease. CT scan suitable for analysis was available from 147 (79%) of the patients. CT density, analysed as the threshold for the lowest 15% of lung voxels, showed statistically significant relationships with the objective physiological parameters of lung function as determined by spirometric Global Initiative for Chronic Obstructive Lung Disease (GOLD) severity staging (p<0.001) and carbon monoxide gas transfer (p<0.01). Density also correlated with subjective measures of quality of life (p=0.02).

CONCLUSIONS

Establishment of the network for data collection and its transfer was highly successful facilitating future collaboration for the study of this rare disease and its management. CT densitometry correlated well with the objective clinical features of the disease supporting its role as the specific marker of the associated emphysema and its severity. Correlations with subjective measures of health, however, were generally weak indicating other factors play a role.

Human Immunodeficiency Virus-Associated Chronic Lung Disease in Children and Adolescents in Zimbabwe: Chest Radiographic and High-Resolution Computed Tomographic Findings

Background

Chronic respiratory symptoms are common among children living with human immunodeficiency virus (HIV). We investigated the radiological features of chronic lung disease in children aged 6–16 years receiving antiretroviral therapy for ≥6 months in Harare, Zimbabwe.

Methods

Consecutive participants from a HIV clinic underwent clinical assessment and chest radiography. Participants with an abnormal chest radiograph (assessed by a clinician) and/or those meeting a clinical case definition for chronic lung disease underwent high-resolution computed tomography (HRCT). Radiological studies were scored independently and blindly by 2 thoracic radiologists. Relationships between radiological abnormalities and lung function were examined.

Results

Among 193 participants (46% female; median age, 11.2 years; interquartile range, 9.0–12.8 years), the median CD4 cell count was 720/µL (473–947/µL), and 79% had a human immunodeficiency virus (HIV) load of <400 copies/mL. The most common chest radiographic finding was ring/tramline opacities (55 of 193 participants; 29%). HRCT scans were evaluated in 84 participants (69%); decreased attenuation (present in 43%) was the dominant abnormality seen. The extent of decreased attenuation was strongly correlated with both the severity and extent of bronchiectasis (r_s = 0.68 and P < .001 for both). The extent of decreased attenuation was also negatively correlated with forced expiratory volume in first second of expiration (r_s = –0.52), forced vital capacity (r_s = –0.42), and forced expiratory flow, midexpiratory phase (r_s = –0.42) (P < .001 for all).

Conclusions

The HRCT findings strongly suggest that obliterative bronchiolitis may be the major cause of chronic lung disease in our cohort. Further studies to understand the pathogenesis and natural history are urgently needed.

Understanding the role of neutrophils in chronic inflammatory airway disease

Airway neutrophilia is a common feature of many chronic inflammatory lung diseases and is associated with disease progression, often regardless of the initiating cause. Neutrophils and their products are thought to be key mediators of the inflammatory changes in the airways of patients with chronic obstructive pulmonary disease (COPD) and have been shown to cause many of the pathological features associated with disease, including emphysema and mucus hypersecretion. Patients with COPD also have high rates of bacterial colonisation and recurrent infective exacerbations, suggesting that neutrophil host defence mechanisms are impaired, a concept supported by studies showing alterations to neutrophil migration, degranulation and reactive oxygen species production in cells isolated from patients with COPD. Although the role of neutrophils is best described in COPD, many of the pathological features of this disease are not unique to COPD and also feature in other chronic inflammatory airway diseases, including asthma, cystic fibrosis, alpha-1 anti-trypsin deficiency, and bronchiectasis. There is increasing evidence for immune cell dysfunction contributing to inflammation in many of these diseases, focusing interest on the neutrophil as a key driver of pulmonary inflammation and a potential therapeutic target than spans diseases. This review discusses the evidence for neutrophilic involvement in COPD and also considers their roles in alpha-1 anti-trypsin deficiency, bronchiectasis, asthma, and cystic fibrosis. We provide an in-depth assessment of the role of the neutrophil in each of these conditions, exploring recent advances in understanding, and finally discussing the possibility of common mechanisms across diseases.

Health status decline in α-1 antitrypsin deficiency: a feasible outcome for disease modifying therapies?

Background

Trials of disease modifying therapies in Chronic Obstructive Pulmonary Disease (COPD) provide challenges for detecting physiological and patient centred outcomes. The purpose of the current study was to monitor decline in health status in Alpha-1 antitrypsin deficiency (AATD) and determine its’ relationship to conventional physiology.

Methods

Patients recruited to the UK-AATD database with a median follow up of 7 years (IQR 5–10) were studied to determine annual change in St George’s Respiratory Questionnaire (SGRQ), FEV₁, gas transfer and their feasibility of use in future trials.

Results

Annual decline in SGRQ had a wide range, was greater for patients with established COPD and correlated with decline in FEV₁ (p < 0.0001). Total score decline was greater (p < 0.05) for those with accelerated FEV₁ decline (median = 1.07 points/year) compared to those without (median = 0.51). Power calculations indicated effective intervention would not achieve MCID for the SGRQ unless the timeframe was extended for up to 8 years. More than 5000 patients/arm would be required for a statistically significant modest effect over 3 years even in those with rapid FEV₁ decline.

Conclusion

Despite AATD being a rapidly declining form of COPD, deterioration in SGRQ was slow consistent with ageing and the chronic nature of disease progression. Power calculations indicate the numbers needed to detect a difference with disease modifying therapies would be prohibitive especially in this rare cause of COPD. These data have important implications for future study design of disease modifying therapies even in COPD not associated with AATD.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0844-6) contains supplementary material, which is available to authorized users.

Alpha-1 antitrypsin deficiency: outstanding questions and future directions

Background

Alpha-1 antitrypsin deficiency (AATD) is a rare hereditary condition that leads to decreased circulating alpha-1 antitrypsin (AAT) levels, significantly increasing the risk of serious lung and/or liver disease in children and adults, in which some aspects remain unresolved.

Methods

In this review, we summarise and update current knowledge on alpha-1 antitrypsin deficiency in order to identify and discuss areas of controversy and formulate questions that need further research.

Results

1) AATD is a highly underdiagnosed condition. Over 120,000 European individuals are estimated to have severe AATD and more than 90% of them are underdiagnosed.

Conclusions

2) Several clinical and etiological aspects of the disease are yet to be resolved. New strategies for early detection and biomarkers for patient outcome prediction are needed to reduce morbidity and mortality in these patients; 3) Augmentation therapy is the only specific approved therapy that has shown clinical efficacy in delaying the progression of emphysema. Regrettably, some countries reject registration and reimbursement for this treatment because of the lack of larger randomised, placebo-controlled trials. 4) Alternative strategies are currently being investigated, including the use of gene therapy or induced pluripotent stem cells, and non-augmentation strategies to prevent AAT polymerisation inside hepatocytes.

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.

Alpha-1 Antitrypsin Deficiency: Phenotypes and Quality of Life

Alpha-1 antitrypsin deficiency (AATD) is a recognized genetic cause of rapidly progressive loss of lung function conventionally assessed by the decline in FEV1. However, there is less information concerning other physiological measures and the impact on quality of life. Data derived predominantly from the UK national registry show that AATD presents with various physiological phenotypes with differing clinical impact and progression. In general, the decline in quality of life is surprisingly slow despite rapid loss of lung function, which may reflect the benefits of centralized services for patients with AATD. Use of the new GOLD classification identifies patient characteristics that relate to mortality and disparate symptomatology despite similar spirometric impairment.

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.

European Respiratory Society statement: diagnosis and treatment of pulmonary disease in α1-antitrypsin deficiency

α1-antitrypsin deficiency (AATD) is the most common hereditary disorder in adults. It is associated with an increased risk of developing pulmonary emphysema and liver disease. The pulmonary emphysema in AATD is strongly linked to smoking, but even a proportion of never-smokers develop progressive lung disease. A large proportion of individuals affected remain undiagnosed and therefore without access to appropriate care and treatment.

The most recent international statement on AATD was published by the American Thoracic Society and the European Respiratory Society in 2003. Since then there has been a continuous development of novel, more accurate and less expensive genetic diagnostic methods. Furthermore, new outcome parameters have been developed and validated for use in clinical trials and a new series of observational and randomised clinical trials have provided more evidence concerning the efficacy and safety of augmentation therapy, the only specific treatment available for the pulmonary disease associated with AATD.

As AATD is a rare disease, it is crucial to organise national and international registries and collect information prospectively about the natural history of the disease. Management of AATD patients must be supervised by national or regional expert centres and inequalities in access to therapies across Europe should be addressed.

Clinical utility of alpha-1 proteinase inhibitor in the management of adult patients with severe alpha-1 antitrypsin deficiency: a review of the current literature

Alpha-1 antitrypsin (AAT) functions primarily to inhibit neutrophil elastase, and its deficiency predisposes individuals to the development of chronic obstructive pulmonary disease (COPD). The putative protective serum concentration is generally considered to be above a threshold of 11 μM/L, and therapeutic augmentation of AAT above this value is believed to retard the progression of emphysema. Several AAT preparations, all derived from human donor plasma, have been commercialized since approval by the US Food and Drug Administration (FDA) in 1987. Biochemical efficacy has been demonstrated by augmentation of pulmonary antiprotease activity, but demonstration of clinical efficacy in randomized, placebo-controlled trials has been hampered by the practical difficulties of performing conventional studies in a rare disease with a relatively long natural history. Computed tomography has been applied to measure lung density as a more specific and sensitive surrogate outcome measure of emphysema than physiologic indices, such as forced expiratory volume in 1 second, and studies consistently show a therapeutic reduction in the rate of lung density decline. However, convincing evidence of benefit using traditional clinical measures remains elusive. Intravenous administration of AAT at a dose of 60 mg/kg/week is the commonest regime in use and has well-documented safety and tolerability. International and national guidelines on the management of AAT deficiency recommend intravenous augmentation therapy to supplement optimized usual COPD treatment in patients with severe deficiency and evidence of lung function impairment.

Treatment of lung disease in alpha-1 antitrypsin deficiency: a systematic review

BACKGROUND

Alpha-1 antitrypsin deficiency (AATD) is a rare genetic condition predisposing individuals to chronic obstructive pulmonary disease (COPD). The treatment is generally extrapolated from COPD unrelated to AATD; however, most COPD trials exclude AATD patients; thus, this study sought to systematically review AATD-specific literature to assist evidence-based patient management.

METHODS

Standard review methodology was used with meta-analysis and narrative synthesis (PROSPERO-CRD42015019354). Eligible studies were those of any treatment used in severe AATD. Randomized controlled trials (RCTs) were the primary focus; however, case series and uncontrolled studies were eligible. All studies had ≥10 participants receiving treatment or usual care, with baseline and follow-up data (>3 months). Risk of bias was assessed appropriately according to study methodology.

RESULTS

In all, 7,296 studies were retrieved from searches; 52 trials with 5,632 participants met the inclusion criteria, of which 26 studies involved alpha-1 antitrypsin augmentation and 17 concerned surgical treatments (largely transplantation). Studies were grouped into four management themes: COPD medical, COPD surgical, AATD specific, and other treatments. Computed tomography (CT) density, forced expiratory volume in 1 s, diffusing capacity of the lungs for carbon monoxide, health status, and exacerbation rates were frequently used as outcomes. Meta-analyses were only possible for RCTs of intravenous augmentation, which slowed progression of emphysema measured by CT density change, 0.79 g/L/year versus placebo (P=0.002), and associated with a small increase in exacerbations 0.29/year (P=0.02). Mortality following lung transplant was comparable between AATD- and non-AATD-related COPD. Surgical reduction of lung volume demonstrated inferior outcomes compared with non-AATD-related emphysema.

CONCLUSION

Intravenous augmentation remains the only disease-specific therapy in AATD and there is evidence that this slows decline in emphysema determined by CT density. There is paucity of data around other treatments in AATD. Treatments for usual COPD may not be as efficacious in AATD, and further studies may be required for this disease group.

Individualized lung function trends in alpha-1-antitrypsin deficiency: a need for patience in order to provide patient centered management?

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by fixed airflow obstruction and accelerated decline of forced expired volume in 1 second (FEV1). Alpha-1-antitrypsin deficiency is a genetic cause of COPD and associated with more rapid decline in lung function, even in some never smokers (NS) but the potential for individualized assessment to reveal differences when compared to group analyses has rarely been considered.

METHODS

We analyzed decline in post-bronchodilator FEV1 and gas transfer (% predicted) over at least 3 years (mean= 6.11, 95% CI 5.80-6.41) in our unique data set of 482 patients with alpha-1-antitrypsin deficiency (PiZ) to determine individual rates of decline, implications for prognosis, and potential clinical management.

FINDINGS

There was a marked variation in individual rates of FEV1 decline from levels consistent with normal aging (observed in 23.5% of patients with established COPD, 57.5% of those without) to those of rapidly declining COPD. Gas transfer did not decline in 12.8% of NS and 20.7% of ex-smokers with established COPD (33.3% and 25.0%, respectively, for those without COPD). There was no correlation between decline in gas transfer and FEV1 for those with COPD, although a weak relationship existed for those without (r=0.218; P<0.025).

CONCLUSION

These data confirm differing individual rates of lung function decline in alpha-1-antitrypsin deficiency, indicating the importance of comprehensive physiological assessment and a personalized approach to patient management.

Antitrypsin Deficiency Assessment and Programme for Treatment (ADAPT): The United Kingdom Registry

The study of rare diseases is compromised by its rarity. The establishment of national and international registries can overcome many of the problems and be used for many monogenetic conditions with relatively consistent outcomes and thus lead to a consistency of clinical management by centres of excellence. However, in Alpha-1 antitrypsin deficiency (AATD), the outcome is highly variable in terms of the organ(s) most affected and the diversity of disease penetration and progression. This creates the added difficulty of understanding the disease sufficiently to monitor and advise the patients to the standard required and importantly design and deliver clinical trials that address the many facets of the disease. The development of research registries and centres of excellence provides the necessary expertise and data to further the understanding and management of diseases like AATD though with significant cost implications. The ADAPT programme was established in 1996 with extensive core funding to enable patients to be seen from all regions of the United Kingdom as an addition to the National Health Service without appointment time constraints and with the purpose of collecting extensive state of the art demographics. The model has proven to be highly productive providing new insights especially into the lung disease, generating and delivering on clinical trials and importantly establishing active patient groups and participation.

Indications for active case searches and intravenous alpha-1 antitrypsin treatment for patients with alpha-1 antitrypsin deficiency chronic pulmonary obstructive disease: an update

The effect of hereditary alpha-1 antitrypsin (AAT) deficiency can manifest clinically in the form of chronic obstructive pulmonary disease (COPD). AAT deficiency (AATD) is defined as a serum concentration lower than 35% of the expected mean value or 50 mg/dl (determined by nephelometry). It is associated in over 95% of cases with Pi*ZZ genotypes, and much less frequently with other genotypes resulting from combinations of Z, S, rare and null alleles. A systematic qualitative review was made of 107 articles, focusing mainly on an active search for AATD in COPD patients and intravenous (iv) treatment with AAT. On the basis of this review, the consultant committee of the Spanish Registry of Patients with AATD recommends that all COPD patients be screened for AATD with the determination of AAT serum concentrations, and when these are low, the evaluation must be completed with phenotyping and, on occasions, genotyping. Patients with severe AATD COPD should receive the pharmacological and non-pharmacological treatment recommended in the COPD guidelines. There is enough evidence from large observational studies and randomized placebo-controlled clinical trials to show that the administration of iv AAT reduces mortality and slows the progression of emphysema, hence its indication in selected cases that meet the inclusion criteria stipulated in international guidelines. The administration of periodic infusions of AAT is the only specific treatment for delaying the progression of emphysema associated with AATD.

Lung Function and CT Densitometry in Subjects with alpha-1-Antitrypsin Deficiency and Healthy Controls at 35 Years of Age

Alpha-1-antitrypsin (AAT) deficiency is a genetic risk factor for pulmonary emphysema. In 1972-74 all 200,000 Swedish new-born infants were screened for AAT deficiency. The aim of the present study was to investigate whether the PiZZ and PiSZ individuals identified by this screening have signs of emphysema and the role of smoking in this, compared with a random sample of control subjects at 35 years of age. The study participants underwent complete pulmonary function tests (PFT) and CT densitometry. The fifteenth percentile density (PD15) and the relative area below -910 HU (RA-910) were analyzed. Fifty-four PiZZ, 21 PiSZ and 66 PiMM control subjects participated in the study. No significant differences were found in lung function between the never-smoking AAT-deficient and control subjects. The 16 PiZZ ever-smokers had significantly lower carbon monoxide transfer coefficient (KCO) than the 20 PiSZ never-smokers (p = 0.014) and the 44 PiMM never-smokers (p = 0.005). After correction for the CT derived lung volume, the PiZZ ever-smokers had significantly lower PD15 (p = 0.046) than the ever-smoking controls. We conclude that 35-year-old PiZZ and PiSZ never-smokers have normal lung function when compared with never-smoking control subjects. The differences in KCO and CT densitometric parameters between the PiZZ ever-smokers and the control subjects may indicate early signs of emphysema.

Alpha-1 antitrypsin deficiency targeted testing and augmentation therapy: a Canadian Thoracic Society clinical practice guideline

Alpha-1 antitrypsin (A1AT) functions primarily to inhibit neutrophil elastase, and deficiency predisposes individuals to the development of chronic obstructive pulmonary disease (COPD). Severe A1AT deficiency occurs in one in 5000 to one in 5500 of the North American population. While the exact prevalence of A1AT deficiency in patients with diagnosed COPD is not known, results from small studies provide estimates of 1% to 5%. The present document updates a previous Canadian Thoracic Society position statement from 2001, and was initiated because of lack of consensus and understanding of appropriate patients suitable for targeted testing for A1AT deficiency, and for the use of A1AT augmentation therapy. Using revised guideline development methodology, the present clinical practice guideline document systematically reviews the published literature and provides an evidence-based update. The evidence supports the practice that targeted testing for A1AT deficiency be considered in individuals with COPD diagnosed before 65 years of age or with a smoking history of <20 pack years. The evidence also supports consideration of A1AT augmentation therapy in nonsmoking or exsmoking patients with COPD (forced expiratory volume in 1 s of 25% to 80% predicted) attributable to emphysema and documented A1AT deficiency (level ≤11 µmol⁄L) who are receiving optimal pharmacological and nonpharmacological therapies (including comprehensive case management and pulmonary rehabilitation) because of benefits in computed tomography scan lung density and mortality.

Association of IREB2 and CHRNA3 polymorphisms with airflow obstruction in severe alpha-1 antitrypsin deficiency

Background

The development of COPD in subjects with alpha-1 antitrypsin (AAT) deficiency is likely to be influenced by modifier genes. Genome-wide association studies and integrative genomics approaches in COPD have demonstrated significant associations with SNPs in the chromosome 15q region that includes CHRNA3 (cholinergic nicotine receptor alpha3) and IREB2 (iron regulatory binding protein 2).

We investigated whether SNPs in the chromosome 15q region would be modifiers for lung function and COPD in AAT deficiency.

Methods

The current analysis included 378 PIZZ subjects in the AAT Genetic Modifiers Study and a replication cohort of 458 subjects from the UK AAT Deficiency National Registry. Nine SNPs in LOC123688, CHRNA3 and IREB2 were selected for genotyping. FEV₁ percent of predicted and FEV₁/FVC ratio were analyzed as quantitative phenotypes. Family-based association analysis was performed in the AAT Genetic Modifiers Study. In the replication set, general linear models were used for quantitative phenotypes and logistic regression models were used for the presence/absence of emphysema or COPD.

Results

Three SNPs (rs2568494 in IREB2, rs8034191 in LOC123688, and rs1051730 in CHRNA3) were associated with pre-bronchodilator FEV₁ percent of predicted in the AAT Genetic Modifiers Study. Two SNPs (rs2568494 and rs1051730) were associated with the post-bronchodilator FEV₁ percent of predicted and pre-bronchodilator FEV₁/FVC ratio; SNP-by-gender interactions were observed. In the UK National Registry dataset, rs2568494 was significantly associated with emphysema in the male subgroup; significant SNP-by-smoking interactions were observed.

Conclusions

IREB2 and CHRNA3 are potential genetic modifiers of COPD phenotypes in individuals with severe AAT deficiency and may be sex-specific in their impact.

Therapeutic efficacy of α-1 antitrypsin augmentation therapy on the loss of lung tissue: an integrated analysis of 2 randomised clinical trials using computed tomography densitometry

Background

Two randomised, double-blind, placebo-controlled trials have investigated the efficacy of IV alpha-1 antitrypsin (AAT) augmentation therapy on emphysema progression using CT densitometry.

Methods

Data from these similar trials, a 2-center Danish-Dutch study (n = 54) and the 3-center EXAcerbations and CT scan as Lung Endpoints (EXACTLE) study (n = 65), were pooled to increase the statistical power. The change in 15^th percentile of lung density (PD15) measured by CT scan was obtained from both trials. All subjects had 1 CT scan at baseline and at least 1 CT scan after treatment. Densitometric data from 119 patients (AAT [Alfalastin^® or Prolastin^®], n = 60; placebo, n = 59) were analysed by a statistical/endpoint analysis method. To adjust for lung volume, volume correction was made by including the change in log-transformed total lung volume as a covariate in the statistical model.

Results

Mean follow-up was approximately 2.5 years. The mean change in lung density from baseline to last CT scan was -4.082 g/L for AAT and -6.379 g/L for placebo with a treatment difference of 2.297 (95% CI, 0.669 to 3.926; p = 0.006). The corresponding annual declines were -1.73 and -2.74 g/L/yr, respectively.

Conclusions

The overall results of the combined analysis of 2 separate trials of comparable design, and the only 2 controlled clinical trials completed to date, has confirmed that IV AAT augmentation therapy significantly reduces the decline in lung density and may therefore reduce the future risk of mortality in patients with AAT deficiency-related emphysema.

Trial registration

The EXACTLE study was registered in ClinicalTrials.gov as 'Antitrypsin (AAT) to Treat Emphysema in AAT-Deficient Patients'; ClinicalTrials.gov Identifier: NCT00263887.

[Dyspnoea and psychopathology in the elderly patient with chronic obstructive pulmonary disease]

Chronic Obstructive Pulmonary Disease (COPD) is a progressive disease with dyspnoea perception as a main symptom. In severe stages, dyspnoea can constitute a risk factor for depression, anxiety and somatization disorders.

OBJECTIVE

The objective was to evaluate the presence of these psychopathologies based on dyspnoea and severity stages in patients with COPD.

MATERIALS AND METHODS

Patients (n = 51) were evaluated by means of the Hospital Anxiety and Depression Scale, the dyspnoea scale (MRC), the General Health Questionnaire (GHQ-28) and spirometric criteria.

RESULTS

The increase in dyspnoea level and disease severity lead to a progressive worsening of anxiety, depressive and somatic symptoms with clinical relevance (P < 0.05). There was a significant correlation between those parameters (P < 0.05).

CONCLUSIONS

The early detection and treatment of these psychopathologies associated with dyspnoea and progression of the disease must be taken into account in this complex pathology.

Emerging drugs for alpha-1-antitrypsin deficiency

IMPORTANCE OF THE FIELD

Alpha-1-antitrypsin (A1AT) deficiency is a common genetic condition that predisposes individuals to the development of chronic obstructive pulmonary disease (COPD) as a direct result of damage caused to the lung by proteolytic enzymes released by migrating neutrophils. The lack of A1AT fails to control these enzymes and in the most common genetic deficiency (Pi Z) is due to accumulation of A1AT in the liver as a result of polymer formation. There is no specific treatment for COPD but understanding the pathophysiology of the disease in A1AT deficiency has led to strategies being used or developed to prevent the lung and liver disease. These strategies may have benefits beyond A1AT deficiency.

AREAS COVERED IN THIS REVIEW

The review covers the history of discovery of the nature and role of A1AT deficiency with particular emphasis on the pathophysiology of the lung disease. Evidence for the role of current therapies is provided together with data of preliminary or experimental strategies that are under development.

WHAT THE READER WILL GAIN

The reader will gain insight into the role of proteinases in the pathophysiology of COPD with particular reference to A1AT deficiency, which is the only human model of the disease. Current evidence of the efficacy of augmentation is provided together with new ways of readdressing the balance between neutrophil proteinases and natural or synthetic inhibitors or repairing lung damage.

TAKE HOME MESSAGE

A1AT deficiency is a good model to investigate the role of inflammation and proteolytic enzymes in the pathophysiology of COPD. Augmentation therapy is expensive but restores the deficiency to normal and current evidence suggests this ameliorates progression of the disease. Understanding the mechanisms involved has led to the development of newer strategies to protect the lung and liver from the development of disease but efficacy and safety concerns require careful introduction of these strategies. Although the condition is relatively common in the Northern hemisphere, the ability to deliver conventional Phase III clinical trials with lung physiology as the primary outcome will be limited by the sensitivity of the tests and number of patients required.

CT lung densitometry in young adults with alpha-1-antitrypsin deficiency

BACKGROUND

Severe (PiZZ) and moderate (PiSZ) alpha-1-antitrypsin (AAT) deficiency predispose to lung emphysema, especially in smokers. We hypothesized that multi-slice computed tomography (CT) might be superior to pulmonary function tests (PFT) to detect lung emphysema in AAT-deficient individuals at the age of 32 years.

METHODS

A subgroup of PiZZ and PiSZ individuals identified during the Swedish newborn screening programme in 1972-74 underwent multi-slice CT and PFT at the age of 32 years. From the CT scans the percentile density at 15% (PD(15)) and the relative area below -910 Hounsfield Units (RA(-910) HU) were calculated. The results of PFT and CT were compared between the AAT-deficient individuals and an age-matched control group.

RESULTS

Twenty-five PiZZ, 11 PiSZ and 17 PiMM individuals participated in the study. All Pi subgroups had normal lung function. The mean PD(15) was 81 (SD 22) g/L in the PiZZ individuals, 96 (SD 35) g/L in the PiSZ individuals and 79 (SD 17) g/L in the PiMM individuals (ns), and the RA-910 were 30 (SD 18)%, 24 (SD 20)%, and 32 (SD 18)%, respectively (ns). For the never-smoker subgroups, in the PiZZ (n = 23), PiSZ (n = 8) and PiMM (n = 12), the mean PD(15) were 95 (SD 35) g/L, 81 (SD 22) g/L, and 75 (SD 12) g/L, respectively (ns). PD(15) was significantly correlated to CT derived lung size (r = -0.72; p < 0.001).

CONCLUSIONS

CT densitometry revealed no signs of emphysema and no differences between the AAT-deficient individuals identified by neonatal screening and age-matched control subjects.

Studies of gamma-glutamyl transferase in alpha-1 antitrypsin deficiency

Gamma-glutamyl transferase (GGT) is a clinical marker of biliary disease, but is also of importance in anti-oxidant metabolic pathways and, consequently, is a potential biomarker of oxidative stress in COPD. Serum GGT is increased in alpha-1 antitrypsin deficiency (AATD) but this could reflect a hepatic, systemic or pulmonary origin. We aimed to investigate the relationship between serum GGT, lung disease, liver disease and mortality in subjects with AATD. Serum GGT was measured at the baseline assessment in 334 PiZ subjects from the UK AATD registry, and related to static lung function, chronic bronchitis, sputum purulence, history of acute exacerbations, smoking status, mortality, alcohol consumption, cirrhosis and serum markers of liver disease. GGT correlated with airflow obstruction and was associated with chronic bronchitis. GGT levels were higher in current smokers compared with ex-smokers and never smokers, and in non-survivors compared with survivors. Although GGT related to alcohol consumption and established liver disease, it was independently related to FEV(1), mortality, smoking history and male gender. In conclusion, although serum GGT reflects the presence of liver disease it is independently associated with airflow obstruction and mortality. Further studies are needed to establish the role of GGT in oxidative lung injury, and its use as a potential biomarker in chronic inflammatory lung disease.

The extent of emphysema in patients with COPD

BACKGROUND AND AIMS

The global initiative for COPD (GOLD) adopted the degree of airway obstruction as a measure of the severity of the disease. The objective of this study was to apply CT to assess the extent of emphysema in patients with chronic obstructive pulmonary disease (COPD) and relate this extent to the GOLD stage of airway obstruction.

MATERIALS AND METHODS

We included 209 patients with COPD. COPD was defined as FEV(1)/FVC < 0.70 and no reversibility to beta(2)-agonists. All patients were current smokers with a smoking history of >or=20 pack-years. Patients were assessed by lung function measurement and visual and quantitative assessment of CT, from which the relative area of emphysema below -910 Hounsfield units (RA-910) was extracted.

RESULTS

Mean RA-910 was 7.4% (n = 5) in patients with GOLD stage I, 17.0% (n = 119) in stage II, 24.2% (n = 79) in stage III and 33.9% (n = 6) in stage IV. Regression analysis showed a change in RA-910 of 7.8% with increasing severity according to GOLD stage (P < 0.001). Combined visual and quantitative assessment of CT showed that 184 patients had radiological evidence of emphysema, whereas 25 patients had no emphysema.

CONCLUSION

The extent of emphysema increases with increasing severity of COPD and most patients with COPD have emphysema. Tissue destruction by emphysema is therefore an important determinant of disease severity in COPD.

Quantitative airway assessment on computed tomography in patients with alpha1-antitrypsin deficiency

The relationship between quantitative airway measurements on computed tomography (CT) and airflow limitation in individuals with severe alpha (1)-antitrypsin deficiency (AATD) is undefined. Thus, we planned to clarify the relationship between CT-based airway indices and airflow limitation in AATD. 52 patients with AATD underwent chest CT and pre-bronchodilator spirometry at three institutions. In the right upper (RUL) and lower (RLL) lobes, wall area percent (WA%) and luminal area (Ai) were measured in the third, fourth, and fifth generations of the bronchi. The severity of emphysema was also calculated in each lobe and expressed as low attenuation area percent (LAA%). Correlations between obtained measurements and FEV(1)% predicted (FEV(1)%P) were evaluated by the Spearman rank correlation test. In RUL, WA% of all generations was significantly correlated with FEV(1)%P (3rd, R = -0.33, p = 0.02; 4th, R = -0.39, p = 0.004; 5th, R = -0.57, p < 0.001; respectively). Ai also showed significant correlations (3rd, R = 0.32, p = 0.02; 4th, R = 0.34, p = 0.01; 5th, R = 0.56, p < 0.001; respectively). Measured correlation coefficients improved when the airway progressed distally from the third to fifth generations. LAA% also correlated with FEV(1)%P (R = -0.51, p < 0.001). In RLL, WA% showed weak correlations with FEV(1)%P in all generations (3rd, R = -0.34, p = 0.01; 4th, R = -0.30, p = 0.03; 5th, R = -0.31, p = 0.03; respectively). Only Ai from the fifth generation significantly correlated with FEV(1)%P in this lobe (R = 0.34, p = 0.01). LAA% strongly correlated with FEV(1)%P (R = -0.71, p < 0.001). We conclude therefore that quantitative airway measurements are significantly correlated with airflow limitation in AATD, particularly in the distal airways of RUL. Emphysema of the lower lung is the predominant component; however, airway disease also has a significant impact on airflow limitation in AATD.

Respiratory bronchiolitis/interstitial lung disease: fibrosis, pulmonary function, and evolving concepts

CONTEXT

The concept of respiratory bronchiolitis/interstitial lung disease (RBILD) was introduced to explain the presence of interstitial lung disease in individuals whose only finding on surgical lung biopsy was smoker's respiratory bronchiolitis (RB). Over time, the diagnostic criteria for RBILD have become progressively more confused.

OBJECTIVE

To review the diagnostic criteria for RBILD.

DESIGN

The review was based on the literature and personal experience.

CONCLUSIONS

The concept of RBILD has changed over time with the recognition that, histologically and radiologically, RB and RBILD are usually indistinguishable. Most authors accept mild alveolar wall fibrosis extending away from the respiratory bronchioles as a part of both RB and RBILD, and occasional cases show quite marked, but probably localized, interstitial fibrosis. What has not been appreciated is that RB is not only an extremely common disease in cigarette smokers but also is ordinarily associated with airflow obstruction. Further, interstitial fibrosis is sometimes found in centrilobular emphysema, and this phenomenon has probably lead to some cases of centrilobular emphysema being misclassified as RB or RBILD. Despite the presence of fibrosis, centrilobular emphysema is still associated with airflow obstruction. We suggest that RBILD be restricted to the clinical setting in which cigarette smokers have a restrictive or mixed obstructive and restrictive functional abnormality, have a marked decrease in diffusing capacity with minimal evidence of airflow obstruction, or have imaging studies showing ground glass opacities/centrilobular nodules plus reticulation and no other lesion besides RB on biopsy to account for these changes. In this setting, the presence of RB-associated interstitial fibrosis probably causes the functional changes.

Exploring the optimum approach to the use of CT densitometry in a randomised placebo-controlled study of augmentation therapy in alpha 1-antitrypsin deficiency

Background

Computed tomography (CT) lung densitometry has been demonstrated to be the most sensitive and specific outcome measure for the assessment of emphysema-modifying therapy, but the optimum densitometric index has yet to be determined and targeted sampling may be more sensitive than whole lung assessment. The EXAcerbations and CT scan as Lung Endpoints (EXACTLE) trial aimed to clarify the optimum approach to the use of CT densitometry data for the assessment of alpha 1-antitrypsin (AAT) augmentation therapy on the progression of emphysema in AAT deficiency (AATD).

Methods

Patients with AATD (n = 77) were randomised to weekly infusions of 60 mg/kg human AAT (Prolastin^®) or placebo over 2 to 2.5 years. Lung volume was included as a covariate in an endpoint analysis and a comparison was made of different CT densitometric indices (15th percentile lung density [PD15], mean lung density [MLD] and voxel index at a threshold of -910 [VI-910] and -950 [VI-950] Hounsfield Units) obtained from whole lung scans at baseline and at 24 to 30 months. Targeted regional sampling was compared with whole lung assessment.

Results

Whole lung analysis of the total change (baseline to last CT scan) compared with placebo indicated a concordant trend that was suggestive of a treatment effect for all densitometric indices (MLD [1.402 g/L, p = 0.204]; VI-910 [-0.611, p = 0.389]; VI-950 [-0.432, p = 0.452]) and that was significant using PD15 (1.472 g/L, p = 0.049). Assessment of the progression of emphysema in the apical, middle and basal regions of the lung by measurement with PD15 showed that this treatment effect was more evident when the basal third was sampled (1.722 g/L, p = 0.040). A comparison between different densitometric indices indicated that the influence of inspiratory variability between scans was greatest for PD15, but when adjustment for lung volume was made this index was the most sensitive measure of emphysema progression.

Conclusion

PD15 is the most sensitive index of emphysema progression and of treatment modification. Targeted sampling may be more sensitive than whole lung analysis.

Trial registration

Registered in ClinicalTrials.gov as 'Antitrypsin (AAT) to Treat Emphysema in AAT-Deficient Patients'; ClinicalTrials.gov Identifier: NCT00263887.

Imaging in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is divided into pulmonary emphysema and chronic bronchitis (CB). Emphysema is defined patho-anatomically as "permanent enlargement of airspaces distal to the terminal bronchiole, accompanied by the destruction of their walls, and without obvious fibrosis" (1). These lesions are readily identified and quantitated using computed tomography (CT), whereas the accompanying hyperinflation is best detected on plain chest X-ray, especially in advanced disease. The diagnosis of CB is clinical and relies on the presence of productive cough for 3 months in 2 or more successive years. The pathological changes of mucosal inflammation and bronchial wall thickening have been more difficult to identify with available imaging techniques. However, recent studies using Multi-detector row CT (MDCT) reported more reproducible assessment of air wall thickening.

Matrix metalloprotease polymorphisms are associated with gas transfer in alpha 1 antitrypsin deficiency

Alpha-1-antitrypsin deficiency (AATD) is associated with variable development of emphysema and other features of chronic obstructive pulmonary disease (COPD). Matrix metalloproteinases (MMPs) are believed to be important in the pathophysiology of COPD, and may therefore confer susceptibility to this phenotype in patients with AATD.

Objectives: to assess the role of polymorphism of MMP1, MMP3 and MMP12 in AATD phenotypes.

Methods: 424 PiZZ subjects from the UK AATD Registry were assessed for history of chronic bronchitis (CB), post-bronchodilator lung function impairment and decline of lung function. Tag single nucleotide polymorphisms (SNPs) for MMP1, MMP3 and MMP12 were chosen using HapMap (r2>0.8, MAF>0.05) and were genotyped using TaqMan® genotyping technologies. Quantitative genetic association was assessed using regression modelling to correct for covariates.

Results: in patients with AATD, carriers of the G allele of rs678815 ( MMP3) had lower gas transfer (KCO) ( P = 0.025, B =-7.766) than the homozygous wild type, while carriers of the T allele of rs470358 ( MMP1) had higher KCO ( P = 0.025, B = 6.130).

Conclusions: variations in MMP1 and MMP3 are associated with gas transfer in AATD, supporting a previous family study showing linkage of KCO to this gene region. Replication of these preliminary data is now required particularly if MMP inhibitors are to be considered as a therapeutic option.

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

Computed tomographic based indices of emphysematous lung destruction may highlight differences in disease pathogenesis and further enable the classification of subjects with Chronic Obstructive Pulmonary Disease. While there are multiple techniques that can be utilized for such radiographic analysis, there is very little published information comparing the performance of these methods in a clinical case series. Our objective was to examine several quantitative and semi-quantitative methods for the assessment of the burden of emphysema apparent on computed tomographic scans and compare their ability to predict lung mechanics and function. Automated densitometric analysis was performed on 1094 computed tomographic scans collected upon enrollment into the National Emphysema Treatment Trial. Trained radiologists performed an additional visual grading of emphysema on high resolution CT scans. Full pulmonary function test results were available for correlation, with a subset of subjects having additional measurements of lung static recoil. There was a wide range of emphysematous lung destruction apparent on the CT scans and univariate correlations to measures of lung function were of modest strength. No single method of CT scan analysis clearly outperformed the rest of the group. Quantification of the burden of emphysematous lung destruction apparent on CT scan is a weak predictor of lung function and mechanics in severe COPD with no uniformly superior method found to perform this analysis. The CT based quantification of emphysema may augment pulmonary function testing in the characterization of COPD by providing complementary phenotypic information.

The TNFalpha gene relates to clinical phenotype in alpha-1-antitrypsin deficiency

BACKGROUND

Genetic variation may underlie phenotypic variation in chronic obstructive pulmonary disease (COPD) in subjects with and without alpha 1 antitrypsin deficiency (AATD). Genotype specific sub-phenotypes are likely and may underlie the poor replication of previous genetic studies. This study investigated subjects with AATD to determine the relationship between specific phenotypes and TNFalpha polymorphisms.

METHODS

424 unrelated subjects of the PiZZ genotype were assessed for history of chronic bronchitis, impairment of lung function and radiological presence of emphysema and bronchiectasis. A subset of subjects with 3 years consecutive lung function data was assessed for decline of lung function. Four single nucleotide polymorphisms (SNPs) tagging TNFalpha were genotyped using TaqMan(R) genotyping technologies and compared between subjects affected by each phenotype and those unaffected. Plasma TNFalpha levels were measured in all PiZZ subjects.

RESULTS

All SNPs were in Hardy-Weinberg equilibrium. A significant difference in rs361525 genotype (p = 0.01) and allele (p = 0.01) frequency was seen between subjects with and without chronic bronchitis, independent of the presence of other phenotypes. TNFalpha plasma level showed no phenotypic or genotypic associations.

CONCLUSION

Variation in TNFalpha is associated with chronic bronchitis in AATD.

Correlation between high-resolution computed tomography features and patients' characteristics in chronic obstructive pulmonary disease

BACKGROUND

During the last few decades, high-resolution computed tomography (HRCT) has come up as a new diagnostic modality to diagnose emphysematous and chronic bronchitis components of chronic obstructive pulmonary disease (COPD). The present study was undertaken to evaluate for various quantitative and qualitative HRCT features in patients with COPD, and to detect patients' characteristics that correlate with these HRCT features.

MATERIALS AND METHODS

Forty male patients with COPD attending the COPD clinic at a tertiary referral hospital and postgraduate medical institute were included in the study. Various HRCT features, including tracheal index, thoracic cage ratio, sterno-aortic distance, thoracic cross-sectional area, vascular attenuation, vascular distortion, mosaic attenuation pattern, and directly visible small airways, were evaluated and correlated with patients' characteristics, including age, duration of illness, quantum of smoking, dyspnea score, quality-of-life index, and various spirometric indices.

RESULTS

We found significant correlations of various quantitative and qualitative HRCT features with age, duration of illness, quantum of smoking, quality-of-life index, and the spirometric indices showing the extent of airways obstruction.

CONCLUSIONS

Various quantitative and qualitative HRCT features were found to correlate with patients' characteristics, spirometric indices, and health-related quality-of-life score, suggesting that HRCT is useful not only in detecting emphysema and its various subtypes but also in predicting the extent and severity of COPD.

Detection of emphysema progression in alpha 1-antitrypsin deficiency using CT densitometry; methodological advances

BACKGROUND

Computer tomography (CT) densitometry is a potential tool for detecting the progression of emphysema but the optimum methodology is uncertain. The level of inspiration affects reproducibility but the ability to adjust for this variable is facilitated by whole lung scanning methods. However, emphysema is frequently localised to sub-regions of the lung and targeted densitometric sampling may be more informative than whole lung assessment.

METHODS

Emphysema progression over a 2-year interval was assessed in 71 patients (alpha 1-antitrypsin deficiency with PiZ phenotype) with CT densitometry, using the 15th percentile point (Perc15) and voxel index (VI) -950 Hounsfield Units (HU) and -910 HU (VI -950 and -910) on whole lung, limited single slices, and apical, central and basal thirds. The relationship between whole lung densitometric progression (DeltaCT) and change in CT-derived lung volume (DeltaCTVol) was characterised, and adjustment for lung volume using statistical modelling was evaluated.

RESULTS

CT densitometric progression was statistically significant for all methods. DeltaCT correlated with DeltaCTVol and linear regression indicated that nearly one half of lung density loss was secondary to apparent hyperinflation. The most accurate measure was obtained using a random coefficient model to adjust for lung volume and the greatest progression was detected by targeted sampling of the middle third of the lung.

CONCLUSION

Progressive hyperinflation may contribute significantly to loss of lung density, but volume effects and absolute tissue loss can be identified by statistical modelling. Targeted sampling of the middle lung region using Perc15 appears to be the most robust measure of emphysema progression.