Screening for alpha1-Pi deficiency in patients with lung diseases

Prevalence of α1-antitrypsin PiZZ genotypes in patients with COPD in Europe: a systematic review

The percentage of α₁-antitrypsin protease inhibitor ZZ (PiZZ) genotypes in patients with COPD is controversial, with large differences among various studies. We aimed to estimate the prevalence of PiZZ in COPD patients from 20 European countries with available data, according to the number of PiZZ and COPD individuals in each country.

A systematic review was conducted to select European countries with reliable data on the prevalence of PiZZ and COPD. We created a database with the following data: 1) total population and population aged ≥40 years according to the Eurostat database; 2) number and 95% CI of PiZZ patients aged ≥40 years; 3) application of a conversion factor of genetic penetrance of 60%; 4) number of COPD individuals, with 95% CI, aged ≥40 years; and 5) calculation of the PiZZ/COPD ratio. Finally, results were presented using an Inverse Distance Weighted Interpolation map.

We found 36 298 (95% CI 23 643–56 594) PiZZ individuals at high risk and 30 849 709 (95% CI 21 411 293–40 344 496) COPD patients, with a PiZZ/COPD ratio of 0.12% (range 0.08–0.24%), and a prevalence of 1 out of 408 in Northern, 1 out of 944 in Western, 1 out of 1051 in Central, 1 out of 711 in Southern, and 1 out of 1274 in Eastern Europe.

These data may be useful to plan strategies for future research and diagnosis, and to rationalise the available therapeutic resources.

There is a significant number of PiZZ individuals at high risk of COPD, as well as an impressive number of patients with COPD in Europe. The ratio between PiZZ and COPD ranges between 0.08% and 0.24%, with wide differences among countries.https://bit.ly/2VrOzUv

Prevalence of Alpha-1 Antitrypsin Deficiency in COPD Patients in Argentina. The DAAT.AR Study

INTRODUCTION

Alpha-1 antitrypsin deficiency (AATD) is still underdiagnosed, despite the recommendation to determine AAT in patients with chronic obstructive pulmonary disease (COPD).

OBJECTIVE

To estimate the prevalence of AATD in COPD patients adjusted according to the population of the COPD prevalence study in Argentina (EPOC.AR).

MATERIAL AND METHODS

This was a multicenter prospective cross-sectional study of a population aged≥30 years of age diagnosed with COPD, involving AAT quantification in dry blood spot and subsequent genotyping in subjects with<1.5mg/dL AAT in dry blood spot (<80mg/dL in serum). AAT was defined as the detection of variants ZZ or SZ on genotyping. The EPOC.AR study population was used to calculate local adjusted prevalence.

RESULTS

We included 3,254 patients (544 with AAT<80mg/dL) with a spirometric diagnosis of COPD. The prevalence of AATD in the total study population was 1.29% (95% CI 0.93-1.74), of which 0.92% (95% CI 0.62-1.31) were Pi*ZZ and 0.37% (95% CI 0.19-0.64) Pi*SZ. The adjusted prevalence of AATD in COPD patients≥40 years of age was 0.83% (95% CI 0.23-2.08). We found that AATD was negatively associated with age (OR 0.94; 95% CI 0.90-0.98; P=.006), smoking habit (OR 0.98; 95% CI 0.96-0.99; P=.009), and FEV₁% (OR 0.95; 95% CI 0.91-0.99; P=.015).

CONCLUSIONS

The prevalence of AATD in the adult population with COPD in Argentina is estimated to be 0.83%, which could represent 17,000 cases in our country.

Portuguese consensus document for the management of alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin deficiency (AATD) is a genetic autosomal codominant disorder caused by mutations in SERPINA1 gene. It is one of the most prevalent genetic disorders, although it remains underdiagnosed. Whereas at international level there are several areas of consensus on this disorder, in Portugal, inter-hospital heterogeneity in clinical practice and resources available have been adding difficulties in reaching a diagnosis and in making therapeutic decisions in this group of patients. This raised a need to draft a document expressing a national consensus for AATD. To this end, a group of experts in this field was created within the Portuguese Pulmonology Society - Study group on AATD, in order to elaborate the current manuscript. The authors reviewed the existing literature and provide here general guidance and extensive recommendations for the diagnosis and management of AATD that can be adopted by Portuguese clinicians from different areas of Medicine. This article is part of a supplement entitled "Portuguese consensus document for the management of alpha-1-antitrypsin deficiency" which is sponsored by Sociedade Portuguesa de Pneumologia.

Real world evaluation of a novel lateral flow assay (AlphaKit® QuickScreen) for the detection of alpha-1-antitrypsin deficiency

BACKGROUND

Alpha-1-Antitrypsin (AAT) deficiency (AATD) is a hereditary disorder that manifests primarily as pulmonary emphysema and liver cirrhosis. The clinically most relevant mutation causing AATD is a single nucleotide polymorphism Glu342Lys (Z-mutation). Despite the recommendation to test every COPD patient, the condition remains severely underdiagnosed with a delay of several years between first symptoms and diagnosis. The Grifols' AlphaKit® QuickScreen is a novel qualitative point-of-care (POC) in vitro screening test developed for the detection of the Z AAT protein in capillary whole blood. The objective of this prospective, international, multi-center, diagnostic, interventional real-world study was to assess the performance of this device for the detection of AATD in test-naïve COPD patients.

METHODS

1044 test-naïve COPD patients were recruited from 9 centers in Spain and 10 centers in Germany, ranging from primary to tertiary care. To evaluate the performance of the test, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated compared with the gold standard (genotyping).

RESULTS

Genotyping and phenotyping of all 1019 evaluable samples revealed 4.12% of patients as carriers of at least one Z-allele, while 0.29% carried the homozygous genotype Pi*ZZ. The evaluation of the test's ability to detect the PiZ protein yielded the following results: specificity 97.8%, sensitivity 73.8%, negative predictive value 98.9%, and positive predictive value 58.5%. All false negatives (n = 11) were heterozygote Pi*MZ samples.

CONCLUSIONS

The tested device can be used as an appropriate tool to exclude AATD in primary care and in the overall COPD population, except in patients with a high a-priori- probability of AATD.

COPD in individuals with the PiMZ alpha-1 antitrypsin genotype

Since the discovery of severe alpha-1 antitrypsin deficiency as a genetic risk factor for emphysema, there has been ongoing debate over whether individuals with intermediate deficiency with one protease inhibitor Z allele (PiMZ, or MZ) are at some risk for emphysema. This is important, because MZ individuals comprise 2-5% of the general population. In this review we summarise the evidence about the risks of the MZ population to develop emphysema or asthma. We discuss the different study designs that have tried to answer this question. The risk of emphysema is more pronounced in case-control than in population-based studies, perhaps due to inadequate power. Carefully designed family studies show an increased risk of emphysema in MZ smokers. This is supported by the rapid decline in lung function of MZ individuals when compared to the general population after massive environmental exposures. The risk of asthma in MZ subjects is less studied, and more literature is needed before firm conclusions can be made. Augmentation therapy in MZ individuals is not supported by any objective studies. MZ smokers are at increased risk for emphysema that is more pronounced when other environmental challenges are present.

The prevalence of PI*S and PI*Z SERPINA1 alleles in healthy individuals and COPD patients in Saudi Arabia: A case-control study

Alpha-1 antitrypsin (AAT) is an acute phase protein produced in hepatocytes. Its deficiency affects the lungs and liver. A case-control study was carried out to determine the prevalence of 2 common deficiency alleles, PI*S and PI*Z, for alpha-1 antitrypsin deficiency (AATD) in both healthy and chronic obstructive pulmmonary disease (COPD)-affected Saudi populations and to clarify the importance of genetic tests in the screening of people at risk for COPD.One thousand blood samples from healthy individuals and 1000 from COPD-affected Saudi individuals were genotyped for the above-mentioned alleles, using real-time polymerase chain reaction (PCR), with the exclusion of any other nationalities. Data were analyzed by determining the allele and genotype frequencies through gene counting and its confidence intervals. The allele frequencies, derived by the Hardy-Weinberg equilibrium method, were analyzed by Pearson Chi-squared tests. The confidence intervals for genotype frequencies were calculated using exploratory software for confidence intervals.Of the 1000 COPD patients included in our study, the prevalence of PI*S and PI*Z was 21.8% and 7.7%, respectively, while within the 1000 normal samples, these alleles occurred in 8.9% of patients for PI*S and 1.6% for PI*Z. The AAT deficiency genotype frequencies (PI*ZZ, PI*SS, and PI*SZ) were 6.5 per 1000 and 87 per 1000 for normal and COPD-affected Saudi individuals.Our results indicated a high prevalence of AATD alleles in the normal Saudi population and an association between AAT deficiency and pulmonary disease development. Additionally, our research confirms the importance of genetic screening to achieve early and accurate diagnosis of AATD.

Selected metabolic aspects of elastin and collagen fiber proteolysis in diseases of the respiratory system - the significance of α1 antitrypsin deficiency

The process of elastin and collagen fiber destruction was presented based on the example of the changes taking place in the course of chronic obstructive pulmonary disease and primary spontaneous pneumothorax. In 1963, when analyzing patients with α1 antitrypsin deficiency, Dr Laurell and Dr Eriksson hypothesized that elastolysis plays a role in the pathogenesis of emphysema, which marked the beginning of studies aimed at analyzing this process. The present work concerns new scientific reports regarding the hypothesis. The most important risk factors include protease-antiprotease imbalance and α1 antitrypsin protein deficiency.

Results from a large targeted screening program for alpha-1-antitrypsin deficiency: 2003 - 2015

Background

Alpha-1-antitrypsin deficiency (AATD) is an autosomal codominant inherited disease that is significantly underdiagnosed. We have previously shown that the combination of an awareness campaign with the offer of free diagnostic testing results in the detection of a relevant number of severely deficient AATD patients. The present study provides an update on the results of our targeted screening program (German AAT laboratory, University of Marburg) covering a period from August 2003 to May 2015.

Methods

Diagnostic AATD detection test kits were offered free of charge. Dried blood samples were sent to our laboratory and used for the semiquantitative measurement of the AAT-level (nephelometry) and the detection of the S- or Z-allele (PCR). Isoelectric focusing was performed when either of the initial tests was indicative for at least one mutation. Besides, we evaluated the impact of additional screening efforts and the changes of the detection rate over time, and analysed the relevance of clinical parameters in the prediction of severe AATD.

Results

Between 2003 and 2015, 18,638 testing kits were analysed. 6919 (37.12 %) carried at least one mutation. Of those, we identified 1835 patients with severe AATD (9.82 % of the total test population) including 194 individuals with rare genotypes. Test initiatives offered to an unselected population resulted in a dramatically decreased detection rate. Among clinical characteristics, a history of COPD, emphysema, and bronchiectasis were significant predictors for Pi*ZZ, whereas a history of asthma, cough and phlegm were predictors of not carrying the genotype Pi*ZZ.

Conclusion

A targeted screening program, combining measures to increase awareness with cost-free diagnostic testing, resulted in a high rate of AATD detection. The clinical data suggest that testing should be primarily offered to patients with COPD, emphysema, and/or bronchiectasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-016-0453-8) contains supplementary material, which is available to authorized users.

Diagnosis of alpha-1 antitrypsin deficiency: a population-based study

INTRODUCTION

Alpha-1 antitrypsin deficiency (AATD) remains an underdiagnosed condition despite initiatives developed to increase awareness. The objective was to describe the current situation of the diagnosis of AATD in primary care (PC) in Catalonia, Spain.

METHODS

We performed a population-based study with data from the Information System for Development in Research in Primary Care, a population database that contains information of 5.8 million inhabitants (80% of the population of Catalonia). We collected the number of alpha-1 antitrypsin (AAT) determinations performed in the PC in two periods (2007-2008 and 2010-2011) and described the characteristics of the individuals tested.

RESULTS

A total of 12,409 AAT determinations were performed (5,559 in 2007-2008 and 6,850 in 2010-2011), with 10.7% of them in children. As a possible indication for AAT determination, 28.9% adults and 29.4% children had a previous diagnosis of a disease related to AATD; transaminase levels were above normal in 17.7% of children and 47.1% of adults. In total, 663 (5.3%) individuals had intermediate AATD (50-100 mg/dL), 24 (0.2%) individuals had a severe deficiency (<50 mg/dL), with a prevalence of 0.19 cases of severe deficiency per 100 determinations. Nine (41%) of the adults with severe deficiency had a previous diagnosis of COPD/emphysema, and four (16.7%) were diagnosed with COPD within 6 months.

CONCLUSION

The number of AAT determinations in the PC is low in relation to the prevalence of COPD but increased slightly along the study period. The indication to perform the test is not always clear, and patients detected with deficiency are not always referred to a specialist.

The use of mass spectrometry to analyze dried blood spots

Dried blood spots (DBS) typically consist in the deposition of small volumes of capillary blood onto dedicated paper cards. Comparatively to whole blood or plasma samples, their benefits rely in the fact that sample collection is easier and that logistic aspects related to sample storage and shipment can be relatively limited, respectively, without the need of a refrigerator or dry ice. Originally, this approach has been developed in the sixties to support the analysis of phenylalanine for the detection of phenylketonuria in newborns using bacterial inhibition test. In the nineties tandem mass spectrometry was established as the detection technique for phenylalanine and tyrosine. DBS became rapidly recognized for their clinical value: they were widely implemented in pediatric settings with mass spectrometric detection, and were closely associated to the debut of newborn screening (NBS) programs, as a part of public health policies. Since then, sample collection on paper cards has been explored with various analytical techniques in other areas more or less successfully regarding large-scale applications. Moreover, in the last 5 years a regain of interest for DBS was observed and originated from the bioanalytical community to support drug development (e.g., PK studies) or therapeutic drug monitoring mainly. Those recent applications were essentially driven by improved sensitivity of triple quadrupole mass spectrometers. This review presents an overall view of all instrumental and methodological developments for DBS analysis with mass spectrometric detection, with and without separation techniques. A general introduction to DBS will describe their advantages and historical aspects of their emergence. A second section will focus on blood collection, with a strong emphasis on specific parameters that can impact quantitative analysis, including chromatographic effects, hematocrit effects, blood effects, and analyte stability. A third part of the review is dedicated to sample preparation and will consider off-line and on-line extractions; in particular, instrumental designs that have been developed so far for DBS extraction will be detailed. Flow injection analysis and applications will be discussed in section IV. The application of surface analysis mass spectrometry (DESI, paper spray, DART, APTDCI, MALDI, LDTD-APCI, and ICP) to DBS is described in section V, while applications based on separation techniques (e.g., liquid or gas chromatography) are presented in section VI. To conclude this review, the current status of DBS analysis is summarized, and future perspectives are provided.

Alpha-1-antitrypsin deficiency: increasing awareness and improving diagnosis

Alpha-1-antitrypsin deficiency (AATD) is a hereditary disorder that is characterized by a low serum level of alpha-1-antitrypsin (AAT). The loss of anti-inflammatory and antiproteolytic functions, together with pro-inflammatory effects of polymerized AAT contribute to protein degradation and increased inflammation resulting in an increased risk of developing chronic obstructive pulmonary disease (COPD) and emphysema, especially in smokers. AATD is a rare disease that is significantly underdiagnosed. According to recent data that are based on extrapolations, in many countries only 5-15% of homozygous individuals have been identified. Furthermore, the diagnostic delay typically exceeds 5 years, resulting in an average age at diagnosis of about 45 years. Although the American Thoracic Society/European Respiratory Society recommendations state that all symptomatic adults with persistent airway obstruction should be screened, these recommendations are not being followed. Potential reasons for that include missing knowledge about the disease and the appropriate tests, and the low awareness of physicians with regard to the disorder. Once the decision to initiate testing has been made, a screening test (AAT serum level or other) should be performed. Further diagnostic evaluation is based on the following techniques: polymerase chain reaction (PCR) for frequent and clinically important mutations, isoelectric focusing (IEF) with or without immunoblotting, and sequencing of the gene locus coding for AAT. Various diagnostic algorithms have been published for AATD detection (severe deficiency or carrier status). Modern laboratory approaches like the use of serum separator cards, a lateral flow assay to detect the Z-protein, and a broader availability of next-generation sequencing are recent advances, likely to alter existing algorithms.

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.

Targeted screening programmes in COPD: how to identify individuals with α1-antitrypsin deficiency

α₁-antitrypsin deficiency (AATD) is a significantly under-recognised autosomal genetic disorder with <10% of affected individuals being clinically diagnosed. Moreover, rigorous genetic epidemiological data regarding AATD are lacking. The majority of findings come from the USA and Western Europe, and no information is available for many countries. To address this concern, an α₁-antitrypsin (AAT) laboratory was set up in 2009 at the National Institute of Tuberculosis and Lung Diseases (Warsaw, Poland). In 2010, an AATD screening programme targeting patients with respiratory disorders was initiated in Poland. This targeted survey has provided valuable information regarding AAT-deficient genotypes, clinical disease and levels of expertise at the physician level. After 4 years, almost 2500 patients with chronic obstructive pulmonary disorders have been screened and, in this cohort, ∼13% had AATD alleles. In these patients, the detection frequency for S and Z alleles was four times greater, and the frequency of homozygous PI*ZZ was 16 times greater than that of the general population. These results highlight the need to build awareness in the medical community, and the project is currently being extended to cover central Eastern Europe, with the creation of the Central Eastern European Alpha-1 Antitrypsin Network.

Effective screening and diagnostic strategies for AATD are being implemented across central Eastern Europehttp://ow.ly/H9Ibf

Validation and development of an immunonephelometric assay for the determination of alpha-1 antitrypsin levels in dried blood spots from patients with COPD

OBJECTIVE:

To validate and develop an immunonephelometric assay for the determination of alpha-1 antitrypsin (AAT) levels in dried blood spots from COPD patients in Brazil.

METHODS:

We determined AAT levels in serum samples and dried blood spots from 192 COPD patients. For the preparation of dried blood spots, a disk (diameter, 6 mm) was placed into a tube, eluted with 200 µL of PBS, and stored overnight at 4ºC. All of the samples were analyzed by immunonephelometry in duplicate. We used the bootstrap resampling method in order to determine a cut-off point for AAT levels in dried blood spots.

RESULTS:

The correlation coefficient between the AAT levels in serum samples and those in dried blood spots was r = 0.45. For dried blood spots, the cut-off value was 2.02 mg/dL (97% CI: 1.45-2.64 mg/dL), with a sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 95.7%, 27.2%, and 100%, respectively.

CONCLUSIONS:

This method for the determination of AAT levels in dried blood spots appears to be a reliable screening tool for patients with AAT deficiency.

Alpha-1 antitrypsin deficiency in Iranian patients with chronic obstructive pulmonary disease

Background

Alpha-1 antitrypsin deficiency is a genetic disease which affects both lung and liver. This disease is a recognized factor for chronic obstructive pulmonary disease (COPD). However its importance as the cause of COPD in a country such as Iran is unclear.

Objectives

This study was conducted to find out the role of α-1 antitrypsin deficiency as a cause of COPD in Iranian patients.

Materials and Methods

The serum concentration of α-1 antitrypsin was determined and the genotype of α-1 antitrypsin was also evaluated by PCR-RFLP in 130 patients with COPD and 50 normal healthy blood donors.

Results

No α-1 antitrypsin deficient case was found in normal healthy people and COPD patients.

Conclusions

Our results clarify that deficiency of α-antitrypsin is not a major cause of COPD in Iranian patients.

The challenge of detecting alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin deficiency (AATD) is relatively common but under-recognized. Indeed, fewer than 10% of the estimated 100,000 Americans with AATD have been diagnosed currently, with common reports of long delays between initial symptoms and first detection and the need to see multiple physicians before diagnosis. Because detection can confer benefits (e.g., identification of at-risk family members, lower smoking likelihood, consideration of augmentation therapy), targeted detection of AATD in at-risk groups such as all symptomatic adults with COPD has been endorsed. Two general approaches to detection have been studied: population-based screening (in which testing is performed in a group for whom no increased risk of having AATD exists) and targeted detection or case-finding (in which testing is confined to those with an attributable condition such as COPD or chronic liver disease). Studies to date have suggested that population-based screening is not cost-effective, whereas targeted detection of AATD has been advocated by official society guidelines. Efforts to enhance detection of AATD individuals have included various approaches, including educational campaigns, provision of free test kits, issuance of reminders with medical reports or within an electronic medical record, and empowering respiratory therapists to conduct testing for AATD in pulmonary function laboratories. Such programs have identified individuals with severe deficiency of alpha-1 antitrypsin in up to 12% of subjects, with considerable variation across series by testing criteria. Overall, the persistence of under-recognition of AATD underscores the need for continued efforts to optimize detection of this potentially debilitating genetic disease.

Alpha-1-antitrypsin deficiency in Serbian adults with lung diseases

AIM

Alpha-1-antitrypsin (A1AT) is the main inhibitor of neutrophil elastase, and severe alpha-1-antitrypsin deficiency (A1ATD) is a genetic risk factor for early-onset emphysema. Despite the relatively high prevalence of A1ATD, this condition is frequently underdiagnosed. Our aim was to determine the distribution of the A1ATD phenotypes/alleles in patients with lung diseases as well as in the Serbian population.

METHODS

The study included the adults with chronic obstructive pulmonary disease (COPD) (n=348), asthma (n=71), and bronchiectasis (n=35); the control was 1435 healthy blood donors. The A1ATD variants were identified by isoelectric focusing or polymerase chain reaction-mediated site-directed mutagenesis.

RESULTS

PiMZ heterozygotes, PiZZ homozygotes, and Z allele carriers are associated with significantly higher risk of developing COPD than healthy individuals (odds ratios 3.43, 42.42, and 5.49 respectively). The calculated prevalence of PiZZ, PiMZ, and PiSZ was higher in patients with COPD (1:202, 1:8, and 1:1243) than in the Serbian population (1:5519, 1:38, and 1:5519).

CONCLUSION

The high prevalence of A1ATD phenotypes/allele in our population has confirmed the necessity of screening for A1ATD in patients with COPD. On the other hand, on the basis of the estimated number of those with A1ATD among the COPD patients, it is possible to assess the diagnostic efficiency of A1ATD in the Serbian population.

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.

The prevalence of alpha-1 antitrypsin deficiency among patients found to have airflow obstruction

INTRODUCTION

Alpha-1 antitrypsin deficiency (AATD) is a genetic disease that may be manifested by chronic obstructive pulmonary disease. Despite professional society guidelines that recommend broad testing of at-risk individuals, fewer than 10% of affected individuals have been identified. The goals of this study were to estimate the frequency of abnormal AAT genotypes among patients found to have fixed airflow obstruction and to assess the feasibility of having Pulmonary Function Laboratory personnel administer the study.

METHODS

Nineteen medical centers in the United States participated in the study. Eligible patients (> GOLD II, FEV(1)/FVC ratio < 0.7, with post-bronchodilator FEV(1)<80% predicted) were offered testing for AATD by the Pulmonary Function Laboratory personnel at the time of pulmonary function testing.

RESULTS

A total of 3,457 patients were tested, of whom 3152 were eligible. Deficient patients (ZZ, SZ) constituted 0.63% of subjects, while 10.88% were carriers (MS, MZ). Neither demographic (except African-American race) nor post-bronchodilator pulmonary function variables (FEV(1), FVC, FEV(1)/FVC ratio, TLC, and FEV(1)/FVC) allowed us to predict AAT heterozygote or deficiency status.

CONCLUSIONS

The prevalence of AATD among patients undergoing pulmonary function tests with fixed airflow obstruction was 0.63%. Pulmonary Function Laboratory personnel effectively conducted the study.

Detection of alpha-1 antitrypsin deficiency: a review

Screening studies reveal a much larger number of individuals expected to have alpha-1 antitrypsin deficiency than is clinically recognized, with estimates that only about 2-10% of such individuals have been diagnosed. In the context that recognition of alpha-1 antitrypsin may prompt specific interventions (e.g., smoking avoidance, testing of family members, genetic counseling, and consideration of augmentation therapy), diagnosis is important, inviting much attention for efforts to identify affected individuals. Strategies to identify affected individuals include both population-based screening and targeted detection, and available studies have employed both approaches, though large-scale population-based screening is challenging. As reviewed in this paper, targeted-detection studies have generally produced a higher rate of detecting disease, and tend to be more successful with easier sampling techniques. Strategies to enhance detection in targeted studies have included awareness campaigns, easy testing techniques (such as evaluation of dried blood spots and home, confidential testing), and inclusive criteria for testing which span the full spectrum of clinical manifestations of alpha-1 antitrypsin deficiency.

Augmentation therapy for emphysema due to alpha-1-antitrypsin deficiency

Alpha-1 antitrypsin deficiency (AAT) is a hereditary recessive autosomal disease caused by mutations in the AAT gene. This disease is characterized by abnormally low AAT concentrations in plasma, which, in its homozygote form, carries a high risk for the development of early pulmonary emphysema and liver damage. Since the end of the 1980s augmentation therapy with AAT from human plasma has been available for specific treatment of emphysema due to AAT deficiency. Intravenous augmentation therapy has been demonstrated to be safe and weekly infusions of AAT have resulted in plasma AAT concentrations above those considered protective for the lungs. However, life-long weekly infusions are not well accepted by patients, therefore pharmacokinetic studies have been performed to try to individualize the therapeutic regimen in order to obtain adequate trough serum AAT levels with prolonged intervals of administration. Therapeutic regimens administered every two weeks appear to be safe and result in adequate trough serum concentrations, but less-frequent administrations result in trough levels below the target. Alpha-1-antitrypsin deficiency is largely unrecognized and underdiagnosed. The foundation of national and international registries is a valid strategy to increase awareness about the disease and collect information about the natural history of this deficiency. Furthermore, the identification of a large number of patients will allow the development of new clinical trials aimed at finding better treatments for this infrequent condition.

Laboratory diagnosis of alpha1-antitrypsin deficiency

The laboratory diagnosis of alpha(1)-antitrypsin (AAT) deficiency (AATD) has evolved over the last 40 years since the first cases of the disorder were reported. It is currently performed in specialized centers, and it requires a combination of different biochemical methods: nephelometric AAT concentration, isoelectric focusing, genotyping, and sequencing. The availability of matrices such as the dried blood spot have facilitated the implementation of laboratory analyses for AATD, but they have also challenged laboratories to develop more reliable and reproducible techniques starting from dried blood. In this article, we describe the protocols we have optimized for AATD diagnosis from dried blood spot, in an attempt to hopefully provide useful information for physicians and scientists involved in this diagnostic line. We also describe the diagnostic flowchart for AATD detection that we have developed accordingly.

Alpha-1-Antitrypsin Deficiency: Current Concepts

Since the condition was first described four decades ago, alpha-1-antitrypsin (A1AT) deficiency has served as a model for other disease processes. A1AT is the archetypal serpin designed to ensnare proteases, a process that involves significant conformational change within the molecule. Mutations in the A1AT gene lead to misfolding of the protein and accumulation within the endoplasmic reticulum of hepatocytes resulting in two different pathologic processes. First, the accumulation of mutant A1AT protein has a directly toxic effect on the liver, resulting in hepatitis and cirrhosis. Second, the resultant decrease in circulating A1AT results in protease-antiprotease imbalance at the lung surface and emphysema ensues. A1AT deficiency therefore can be seen as two distinct disease processes: a conformational disease of the liver and a protease-antiprotease imbalance of the lung. This two-stage model of disease in A1AT deficiency is elegant in its simplicity and goes a long way to explaining the clinical manifestations that occur in patients with the condition. However, some aspects of the disease are not readily explained. Recent findings suggest that there is more to the lung damage in A1AT deficiency than simple proteolytic insult and that the presence of the mutant protein itself is proinflammatory and may indeed cause chronic injury to the cells that produce it. This review discusses some of the emerging concepts in alpha-1-antitrypsin research and outlines the implications these new ideas may have for treatment of this condition.

Identification of individuals with alpha-1-antitrypsin deficiency by a targeted screening program

BACKGROUND

Alpha-1-antitrypsin deficiency (AATD) is significantly underdiagnosed. The early detection of AATD would enable affected persons to make lifestyle changes such as quitting smoking. It was the aim of the study to determine whether the combination of an awareness program with the offer of a cost-free diagnostic test results in the identification of a significant number of individuals with severe AATD.

METHODOLOGY

We combined a series of measures to promote awareness with the offer of a diagnostic test at no charge. Test blood was applied to a filter paper and sent to our laboratory. The level of AAT was measured by nephelometry, the presence of the S- or Z-allele was determined by PCR, and phenotyping was performed by isoelectric focusing.

RESULTS

During 37 months 17688 testing kits were distributed and 2722 were sent back to our laboratory. We identified 335 patients with severe AATD including 16 individuals with rare genotypes. Prescreening by determining the AAT serum levels by the submitting physician increased the detection rate as compared to similar programs that screened unselected individuals.

SUMMARY

These data show that the combination of an awareness program with the offer of free diagnostic testing results in the identification of a large number individuals with severe AATD.

[Alpha1-antitrypsin deficiency: situation in Spain and development of a screening program]

Studies undertaken in Spain indicate that 9% of the general population aged between 40 and 70 years is affected by chronic obstructive pulmonary disease (COPD). Although tobacco smoke is the causative factor in more than 90% of cases, it is estimated that only 10% to 20% of smokers develop COPD. This may be explained by the existence of genetic or environmental factors that modulate the toxic effects of tobacco. The best known genetic factor is alpha1-antitrypsin deficiency, which is associated with an increased risk of developing pulmonary emphysema in smokers. The most recent guidelines from both the World Health Organization and the American Thoracic Society/European Respiratory Society recommend the establishment of screening programs for the detection of alpha1-antitrypsin deficiency in patients with COPD. This strategy is crucial in Spain, where the disease is under diagnosed, mainly due to a low index of suspicion among doctors.

Emphysema in alpha1-antitrypsin deficiency: does replacement therapy affect outcome?

Severe alpha(1)-antitrypsin (AAT) deficiency is an inherited disorder that leads to the development of emphysema in smokers at a relatively young age; most are disabled in their forties. Emphysema is caused by the protease-antiprotease imbalance when smoking-induced release of neutrophil elastase in the lung is inadequately inhibited by the deficient levels of AAT, the major inhibitor of neutrophil elastase. This protease-antiprotease imbalance leads to proteolytic damage to lung connective tissue (primarily elastic fibers), and the development of panacinar emphysema. AAT replacement therapy, most often applied by weekly intravenous infusions of AAT purified from human plasma, has been used to partially correct the biochemical defect and raise the serum AAT level above a theoretically protective threshold level of 0.8 g/L. A randomized controlled clinical trial was not considered feasible when purified antitrypsin was released for clinical use. However, AAT replacement therapy has not yet been proven to be clinically effective in reducing the progression of disease in AAT-deficient patients. There was a suggestion of a slower progression of emphysema by computed tomography (CT) scan in a small randomized trial. Two nonrandomized studies comparing AAT-deficient patients already receiving replacement therapy with those not receiving it, and a retrospective study evaluating a decline in FEV(1) before and after replacement therapy, suggested a possible benefit for selected patients. Because of the lack of definitive proof of the clinical effectiveness of AAT replacement therapy and its cost, we recommend reserving AAT replacement therapy for deficient patients with impaired FEV(1) (35-65% of predicted value), who have quit smoking and are on optimal medical therapy but continue to show a rapid decline in FEV(1) after a period of observation of at least 18 months. A randomized placebo-controlled trial using CT scan as the primary outcome measure is required. Screening for AAT deficiency is recommended in patients with chronic irreversible airflow obstruction with atypical features such as early onset of disease or disability in their forties or fifties, or positive family history, and in immediate family members of patients with AAT deficiency.

AAT as a diagnostic tool

Serum alpha-1-antitrypsin (AAT) concentration can be affected by both inflammatory and non-inflammatory conditions. This paper characterizes the nature of AAT in physiology and pathologic deficiency and increasing states. The relationships between the AAT concentration in different clinical materials (serum, urine, faeces) and various diseases connected with different organs were analyzed.

Chronic obstructive pulmonary disease in alpha1-antitrypsin PI MZ heterozygotes: a meta-analysis

BACKGROUND

Severe alpha(1)-antitrypsin deficiency, usually related to homozygosity for the protease inhibitor (PI) Z allele, is a proven genetic risk factor for chronic obstructive pulmonary disease (COPD). The risk of COPD in PI MZ heterozygous individuals is controversial.

METHODS

A search of MEDLINE from January 1966 to May 2003 identified studies that examined the risk of COPD in PI MZ individuals and studies that measured forced expiratory volume in 1 second (FEV(1)) in heterozygotes.

RESULTS

In 16 studies that reported COPD as a categorical outcome, the combined odds ratio (OR) for PI MZ versus PI MM (normal genotype) was 2.31 (95% CI 1.60 to 3.35). The summary OR was higher in case-control studies (OR 2.97; 95% CI 2.08 to 4.26) than in cross sectional studies (OR 1.50; 95% CI 0.97 to 2.31) and was attenuated in studies that adjusted for cigarette smoking (OR 1.61; 95% CI 0.92 to 2.81). In seven studies that reported FEV(1) as a continuous outcome there was no difference in mean FEV(1) between PI MM and PI MZ individuals.

CONCLUSIONS

Case-control studies showed increased odds of COPD in PI MZ individuals, but this finding was not confirmed in cross sectional studies. Variability in study design and quality limits the interpretation. These results are consistent with a small increase in risk of COPD in all PI MZ individuals or a larger risk in a subset. Future studies that adjust for smoking and include other COPD related phenotypes are required to conclusively determine the risk of COPD in PI MZ heterozygotes.