© 2003 American Thoracic Society
American Thoracic Society/European Respiratory Society StatementStandards for the Diagnosis and Management of Individuals with Alpha-1 Antitrypsin DeficiencyTHIS JOINT STATEMENT OF THE AMERICAN THORACIC SOCIETY AND THE EUROPEAN RESPIRATORY SOCIETY WAS APPROVED BY THE ATS BOARD OF DIRECTORS, DECEMBER 2002, AND BY THE ERS EXECUTIVE COMMITTEE, FEBRUARY 2003CONTENTS Executive Summary Introduction, 820 Goals, Organization of the Project, and Timeline, 820 Summary of Main Recommendations Regarding Diagnosis and Management by the Alpha-1 Antitrypsin Deficiency Task Force, 820 Clinical Recognition of AAT Deficiency, 820 Genetic Testing for AAT Deficiency, 821 Liver Disease, 821 Other Conditions, 822 Efficacy of Augmentation Therapy, 822 General Management of Obstructive Lung Disease, 822 References, 822 Lung Disease Preparation of This Document, 823 Introduction, 823 Epidemiology, 823 Pathophysiology of AAT Deficiency, 823 Laboratory Tests, 825 Identification of Individuals with AAT Deficiency, 826 Pathology, 827 Symptoms, 827 Physical Findings, 828 Lung Function Tests, 828 Radiology, Including Computed Tomography and Ventilation–Perfusion Scan, 828 Parameters of Progression: FEV1, Desmosine, and Computed Tomography, 829 Risk Factors, 830 Natural History, 831 Risks of the MZ and SZ Phenotypes for the Development of Emphysema and COPD, 832 Prognosis, 834 Prevention of Lung Disease, 834 Nonspecific Medical Treatment, 834 Augmentation Therapy, 835 Surgical Procedures, 836 Special Situations, 837 Future Directions of Research in AAT Deficiency, 837 Some Specific Research Needs in AAT Deficiency, 838 Appendix 1. Primary Evidence Table: Summary of Studies Addressing Clinical Features of PI*ZZ Alpha-1 Antitrypsin Deficiency, 840 Appendix 2. General Population-based Studies: Prevalence of PI Variants and Risk of Associated Lung Disease, 841 Appendix 3. Chronic Obstructive Pulmonary Disease Population Studies: Prevalence of PI Variants and Risk of Associated Lung Disease, 842 Appendix 4. Serial Case Studies in PI*ZZ: Risk Categories Evaluated, 843 Appendix 5. Studies That Address the Risk of a COPD Family History to PI*MZ Individuals, 845 Appendix 6. Smoking as a Risk Factor for Lung Disease in PI*MZ Individuals, 845 Appendix 7. Environmental Risks of Lung Disease in PI*MZ Individuals, 846 Appendix, 8. PI*MZ Phenotype May Be a Risk Factor for Atopic Disease, 846 Appendix 9. Primary Evidence of Risk of Emphysema in Individuals with PI*SZ Phenotype, 847 Appendix 10. Primary Evidence Table: Summary of Studies Regarding the Efficacy of Augmentation Therapy, 848 References, 849 Liver and Other Diseases Liver Disease, 856 Introduction, 856 Methods, 856 Results, 857 Description of Studies: Number and Types of Reports and Individual Studies, 857 Risk of Liver Disease in PI*ZZ Children, 857 Clinical Manifestations in PI*ZZ Childhood Liver Disease, 858 Risk of Liver Disease in PI*ZZ Adults, 859 Risk of Liver Disease in Adult PI*Z Heterozygotes, 862 Role of Additional Factors for Liver Disease in AAT Deficiency, 863 Risk of Primary Liver Cancer in AAT Deficiency, 863 Risk of Liver Disease in Non-PI*Z Deficiency States, 864 Diagnosis and Management, 864 Follow-Up, 865 Remarks on the Accuracy of Diagnosis of AAT Deficiency: Isoelectric Focusing versus Hepatocytic PAS-D Inclusions, 865 Some Research Goals in AAT Deficiency–related Liver Disease, 866 Some Specific Clinical Research Needs in AAT Deficiency–related Liver Disease, 866 Systemic Vasculitis and Renal Disorders, 866 Multiorgan Vasculitides, 866 Nephropathy, 867 Aneurysmal and Related Diseases, 867 Abdominal Aortic Aneurysms, 867 Intracranial Aneurysms, Extracranial and Intracranial Arterial Dissections, and Fibromuscular Dysplasia, 868 Dermatologic Manifestations, 868 AAT Deficiency–associated Panniculitis, 868 Skin Involvement in Systemic Necrotizing Vasculitides in Severe AAT Deficiency, 869 Other Skin Disorders in Which AAT Deficiency Plays a Role, 869 Miscellaneous Conditions, 869 Exocrine Pancreatic Disease, 869 Endocrine Pancreatic Disease, 869 Celiac Disease, 869 References, 869 Genetic Testing for Alpha-1 Antitrypsin Deficiency: Genetics, Psychosocial, Ethics, and Economics Issues Introduction, 874 Specific Question to Be Addressed, 874 Methods, 874 Data Sources and Search Strategy, 874 Alternative Method of Developing Recommendations, 875 Background: Genetics of AAT Deficiency, 876 Systematic Reviews of the Evidence for the Efficacy of Genetic Testing, 876 Diagnostic Detection Testing, 876 Predispositional Testing of Asymptomatic Individuals at High Risk, 876 Screening Programs, 877 Systematic Reviews of the Individual Issues Relevant for Genetic Testing, 877 Prevalence of AAT Deficiency, 877 Penetrance and Prevalence of AAT Deficiency–related Clinical Disease, 877 Pulmonary Disease, 877 Liver Disease, 877 Necrotizing Panniculitis, 880 Multisystemic Vasculitis, 880 Clinical Impact of AAT Deficiency, 881 Pulmonary Disease, 881 Liver Disease, 882 Necrotizing Panniculitis, 882 Multisystemic Vasculitis, 882 Efficacy of Therapeutic Measures, 882 Pulmonary Disease, 882 Liver Disease, 883 Necrotizing Panniculitis, 883 Accuracy of Genetic Tests for AAT Deficiency, 883 Efficacy of Providing Genetic Risk Information about Changing Health-related Behaviors: Preventive Measures, 885 Cigarette Smoking, 885 Change of Occupation in Response to Receipt of Genetic Information, 886 Psychological Effects of Genetic Testing, 886 Symptomatic Individuals, 886 Asymptomatic Individuals at High Risk, 886 Screening, 888 Adverse Social Effects: Discrimination/Stigma, 888 Economic Costs, 889 Ethical Issues Involved with Genetic Testing, 889 The Requirement for Informed Consent, 889 Overarching Principles, 889 Testing of Children, 890 Do Physicians Have an Ethical and/or Legal Duty to Disclose the Availability of Predictive Genetic Testing to Asymptomatic Individuals?, 891 Research Context, 891 Confidentiality of Genetic Information, 891 Disclosure to Relatives, 891 Recommendations for Genetic Testing, 891 Diagnostic Detection Testing, 892 Predispositional Testing, 895 Carrier Testing in the Reproductive Setting, 895 Screening, 896 References, 896 Membership of the Alpha-1 Antitrypsin Deficiency Task Force FOOTNOTES This statement was developed jointly by an ATS/ERS Task Force. Publication of this Statement was supported, in part, by unrestricted educational grants from the Alpha-1 Foundation and Adventis Behring, LLC. Supported by project funding from the American Thoracic Society, the European Respiratory Society, the American College of Chest Physicians, and the American Association for Respiratory Care. Members of the ad hoc statement committee have disclosed any direct commercial associations (financial relationships or legal obligations) related to the preparation of this statement. This information is kept on file at the ATS headquarters.
ATS/ERSStandards for the Diagnosis and Management of Individuals with Alpha-1 Antitrypsin DeficiencyEXECUTIVE SUMMARY
Introduction In the context of these new developments, a need was felt to reexamine recommendations for optimal management of AAT deficiency, to synthesize current knowledge of diagnosis and management for practicing clinicians, and to identify key remaining questions in need of further investigation. With these purposes in mind, a Task Force to develop a new standards document regarding the diagnosis and management of individuals with severe AAT deficiency was formed in 1998 under the auspices of the American Thoracic Society and the European Respiratory Society, with additional sponsorship and support by the Alpha-1 Foundation, the American College of Chest Physicians, and the American Association for Respiratory Care. Under a contractual arrangement, the Veterans Administration Technology Assessment Program, Office of Patient Care Services, Veterans Health Administration provided education regarding preparing an evidence-based document and support in conducting literature searches. In keeping with current standards for developing evidence-based recommendations for optimal care, the current Task Force has undertaken a systematic review of current literature regarding AAT deficiency. Every effort was made to identify the scientific evidence for positions taken and to identify where there was little or no evidence. In the absence of ratable evidence, consensus among members of the Task Force determined the recommendation. This summary document briefly describes the organization and preparation of the Task Force's report and provides an executive summary of key clinical recommendations. The three following sections are the full systematic reviews prepared by the three individual writing groups that comprised the AAT Deficiency Task Force.
Goals, Organization of the Project, and Timeline A planning group was assembled in the Fall of 1997, when sponsorship and funding by the major sponsors—the American Thoracic Society, the European Respiratory Society, and the Alpha-1 Foundation—was finalized. Additional support from the Alpha-1 Foundation, the American College of Chest Physicians, and the American Association for Respiratory Care allowed the Planning Committee to assemble the full membership of the Task Force and to proceed. As presented in Figure 1, the AAT Deficiency Task Force consisted of an Executive Committee, three individual Writing Groups comprising international experts, and a Steering Committee (composed of the Executive Committee and the Chairs of each of the three Writing Groups). Preparation of the systematic review was aided by members of the Health Care Technology Assessment Program of the Department of Veterans Affairs, who provided ongoing input and guidance to the project regarding literature searches and evidence-based medicine methods. Administrative assistance was provided by the American Thoracic Society. The membership of the Task Force was fully constituted by September 1998, at which point Writing Groups began to review literature and to draft documents for subsequent review by the Steering Committee. The Steering Committee conducted a number of conference calls and five face-to-face meetings between Fall 1998 and Fall 2001 to review the evolving documents. Individual Writing Group documents were finalized by Fall 2001 for final editing by the Executive Committee and subsequent submission to the sponsoring organizations. Reviews were received in June 2002 and the revised document was resubmitted in Fall 2002 for final approval. Approval was granted by the American Thoracic Society in December 2002, when an additional review of salient literature led to a final update of the document. While the Executive Committee has attempted to minimize overlap between the three documents, the Task Force's stated goal of preparing three individual documents, each complete and with its own emphasis, references, and supportive tables and figures, will inevitably lead to some overlap. Finally, in the context that research is ongoing and that current understanding of AAT deficiency and optimal management is evolving, the Task Force recognizes the need for periodic review and updating of management recommendations.
Summary of Main Recommendations Regarding Diagnosis and Management by the Alpha-1 Antitrypsin Deficiency Task Force
Notably, in recognizing the discordance of studies concerning whether bronchiectasis is specifically associated with AAT deficiency, the Task Force recommends discussing AAT testing with individuals who have bronchiectasis without evident etiology, with the understanding that testing could reasonably be accepted or declined.
Genetic testing for AAT deficiency. Recommendations for genetic testing in specific situations were graded from type A to type D (see Table 1). Each recommendation type was based on the level of supportive evidence for each issue regarding testing (e.g., the penetrance of AAT deficiency, population prevalence of AAT deficiency, clinical impact, accuracy of genetic testing, efficacy of treatment, psychologic and social effects, and economic costs) and the weighing by the Task Force of the issues for or against testing. In the context of this grading scheme, recommendations for the four types of genetic testing are as follows.
A type A recommendation for diagnostic testing was made in the following settings:
A type B recommendation for diagnostic testing was made in the following settings:
A type C recommendation for diagnostic testing was made for
2.Predispositional testing. A type A recommendation was made for:
A type B recommendation was made for:
A type D recommendation was made for:
3.Assessment of carrier status in relation to reproduction. A type B recommendation was made for:
4.Population screening. A type D recommendation was made for:
That is, population screening is not recommended currently. However, a possible exception (type B recommendation) regarding population screening may apply in countries satisfying three conditions: (1) the prevalence of AAT deficiency is high (about 1/1,500, or more); (2) smoking is prevalent; and (3) adequate counseling services are available. A type C recommendation was made for:
Liver disease.
Other conditions.
Efficacy of augmentation therapy.
General management of obstructive lung disease.
The scant evidence regarding the efficacy of lung volume reduction surgery (with possible resection of lower lobes) in individuals with AAT deficiency suggests that improvement in dyspnea, lung function, and functional status is possible. However, well-studied, robust selection criteria for ideal candidates remain elusive and the duration of lung volume reduction surgery benefit appears shorter than in individuals with AAT-replete COPD.
REFERENCES
Lung DiseasePREPARATION OF THIS DOCUMENTThis document was prepared by an international committee with representatives of the American Thoracic Society, the European Respiratory Society, and the American College of Chest Physicians. It is intended to be an authoritative guide to physicians and others working in health care, to indicate current understanding of alpha-1 antitrypsin (AAT) deficiency, and the methods for diagnosis and therapy. The literature search involved published work since 1963. For information concerning clinical manifestations, including radiologic characteristics, risk factors, and therapy, studies with the largest cohorts of patients were selected. The evidence for clinical characteristics, risk factors, and therapeutic recommendations was graded as to quality according to the U.S. Preventive Services Task Force (see Table 1) (1).
INTRODUCTION AAT deficiency is a recently discovered hereditary condition, first described in 1963 (2). Intense research over the past 40 years has led to a detailed understanding of the structural genetic abnormalities, pathophysiology of associated pulmonary emphysema, and liver disease and therapeutic approaches for treating the deficiency and managing the associated diseases. The severe deficiency of this protein in serum and in tissues, including lung, occurs as a result of the inheritance of two protease inhibitor deficiency alleles from the AAT gene located on chromosome segment 14q31-32.3 (3, 4). Of the deficiency alleles, PI*Z, is most common and in the homozygous form (PI*ZZ) results in low serum concentrations of AAT protein, usually below 50 mg/dl (less than 11 µM) (5). Pulmonary emphysema of the panacinar type is the most prevalent clinical correlate of this deficiency and is the major cause of disability and death (6). The second most frequent clinical complication is liver disease, usually presenting in infancy as cholestasis, which usually resolves by adolescence (7, 8). However, the most recent data indicate that cirrhosis and carcinoma of the liver affect about 30–40% of patients with AAT deficiency over the age of 50 years and are a significant cause of death in nonsmoking individuals with the PI*ZZ phenotype (9–11). AAT is the protease inhibitor most prevalent in serum. It normally circulates in serum in concentrations of 120–200 mg/dl and was named for its ability to inhibit trypsin. However, its major biological role is to inhibit neutrophil elastase (NE), an enzyme that degrades elastin but also basement membrane and other matrix components (12, 13). AAT is synthesized by hepatocytes and belongs to the serpin family (serine protease inhibitors). The Z variant of the molecule, which is the phenotype most frequently associated with lung disease, results in normal mRNA and rate of synthesis of antitrypsin, but only 15% is released into the circulation. The deficiency occurs because about 85% of synthesized AAT is blocked in the terminal secretory pathway of the hepatocyte (14) and can be seen as large intracellular inclusions in hepatocyte cytoplasm. In the null variants of AAT deficiency, where no AAT protein is produced, there are no inclusions and liver disease is not reported. Through the technique of isoelectric focusing, about 100 genetic variants of AAT have been identified to date. The alphabetical designation to these variants is based on their mobility in an electrophoretic field at alkaline pH. The rapidly migrating variants are designated by the early letters of the alphabet and those migrating more slowly by the later letters, with the Z variant being slowest. The predominant normal phenotype is PI*MM (medium mobility), present in 94–96% of Caucasians (15, 16). Approximately 2–3% of the Caucasian population are heterozygous (PI*MZ). AAT deficiency has been reported in the Far East and Africa, but is relatively rare (17, 18). On the basis of a large survey of studies regarding the occurrence of AAT deficiency worldwide, de Serres estimates that worldwide, 117 million individuals have the PI*MS and PI*MZ phenotypes and that 3.4 million individuals have the PI*ZZ, PI*SZ, or PI*SS phenotype (19). EPIDEMIOLOGY The low frequency of the PI*ZZ phenotype in the general normal population makes firm data collection with respect to prevalence of affected individuals difficult to obtain. However, a number of screening studies have been undertaken (see Appendix 2). The prevalence of AAT deficiency in newborns has been estimated from large population studies, with a screening of all newborns in Sweden in 1972–1974 being the most comprehensive (20). Of 200,000 children in that study, 127 had the PI*ZZ phenotype, yielding a prevalence of approximately 1 in 1,600 newborns. Other studies from Oregon (21), St. Louis (22), and New York (23) have estimated the prevalence to be 1 in 5,097, 1 in 2,857, and 1 in 3,694, respectively. Studies from various regions of Europe have shown a large variation in frequency of the Z gene in different countries (24). The gene frequency for PI type Z is highest on the northwestern seaboard of the European continent and the mutation seems likely to have arisen in southern Scandinavia (24). In the United States, therefore, Z gene frequencies are highest in individuals of northern and western European descent (25). The distribution of S types is quite different; the gene frequency is highest in the Iberian Peninsula and the mutation is likely to have arisen in that region (see Table 2) . (24).
Studies of the prevalence of PI*ZZ, PI*SZ, and PI*MZ patients among patients with a diagnosis of chronic obstructive pulmonary disease (COPD) are summarized in Appendix 3 The range of this prevalence is generally low and variable, depending on the patient population studied, but for PI*ZZ it is 1 to 4.5% and for MZ it can be as high as 17.8%. PATHOPHYSIOLOGY OF AAT DEFICIENCY AAT is a 52-kD single-chain glycoprotein composed of 394 amino acid residues and 3 asparagine-linked complex carbohydrate side chains. The AAT gene spans 12.2 kb on human chromosome 14q31-32.3 and is organized in three noncoding (1a, 1b, and 1c) exons and four (2, 3, 4, and 5) coding exons. The active site of the protein is a single peptide bond, Met358–Ser359, of the AAT sequence and is encoded within exon 5. Hepatocytes are the primary source of AAT but other cells, including mononuclear phagocytes and intestinal and lung epithelial cells, may synthesize the protein. The major function of AAT is to inhibit a variety of serine proteinases, but kinetic studies have shown that the preferential target is neutrophil elastase (NE), an omnivorous 29-kD extracellular endopeptidase. Inhibition occurs by forming stable 1:1 equimolar complexes in which the proteinase binds to the AAT active site (26) (see Figure 1 , which depicts the molecular interactions of inhibition).
The human neutrophil also contains and secretes a second potent elastase called proteinase-3 (PR-3). Also a serine protease, PR-3 degrades elastin in vitro and causes emphysema when administered intratracheally to hamsters (27). The NH2-terminal amino acid sequence of PR-3 is identical to that of the target antigen of the anti-neutrophil cytoplasmic autoantibodies associated with Wegener's granulomatosis, also called antiproteinase-3-positive vasculitis in accompanying documents (28). Proteinase-3 is inhibited by AAT and by  2-macroglobulin but not by secretory leukoprotease inhibitor (28). AAT is a highly pleiomorphic protein, thus reflecting a pleiomorphic gene locus, with roughly 100 alleles having been identified to date. Variants are codominantly inherited and are classified according to the protease inhibitor (PI) system, as defined by plasma isoelectric focusing. AAT genotypes that confer an increased risk for developing pulmonary emphysema are those in which deficiency or null alleles are combined in homozygous or heterozygous states, which encode AAT plasma levels below a protective threshold, that is, 11 µmol/L (29). On the basis of plasma levels and function of AAT, variants are categorized into the following:
The gene or protein sequences of most variants have been characterized. The mechanism of the commonest AAT deficiency is related to conformational changes of the Z AAT, which spontaneously transforms its reactive loop into a ß-sheet polymer under physiological conditions (32). Polymers with identical appearance have been isolated from the liver of a Z AAT homozygote. The pathogenesis of pulmonary emphysema in AAT deficiency and as a consequence of cigarette smoking in individuals with normal levels of AAT has been postulated to be caused by a protease–antiprotease imbalance. The protease–antiprotease imbalance hypothesis proposes that pulmonary emphysema in AAT deficiency occurs because of an imbalance between the antielastase defenses of the lung and the relatively excessive action of leukocyte elastase, leading to degradation of elastin and other extracellular matrix components of the lower respiratory tract. This hypothesis is based on evidence that AAT is a major antielastase defense in the alveolar spaces, and that severely AAT-deficient subjects have little or no AAT in their alveoli and are prone to develop destructive emphysema (33). Such evidence has been corroborated over the years by a range of experimental data. Surveys of large series of patients have clearly shown that fewer than 60% of individuals with severe AAT deficiency develop significant airflow limitation (6). This suggests that in many cases, AAT deficiency alone is not enough to induce emphysema (34). It has also been suggested that pulmonary emphysema develops when elastin fiber repair mechanisms are overwhelmed by a massive attack of elastases from inflammatory reactions (35). A major pathogenic factor is cigarette smoke, which contains oxidants capable of inactivating AAT by converting active site Met358 to methionine sulfoxide, with the association constant for NE being reduced about 2,000-fold. In addition, it has been shown that Z AAT inhibits NE at a slower rate than does M AAT (4.5 versus 9 x 106 M–1 second–1) (36). Furthermore, AAT polymers can be detected in the bronchoalveolar lavage fluid, as demonstrated in two of five subjects with emphysema related to PI*ZZ AAT deficiency (37). Because polymerization obscures the AAT reactive loop, the conformational transition may impair the inhibitory activity. Therefore, in AAT deficiency, oxidants contained in cigarette smoke may further impair a quantitatively and qualitatively less functional AAT. In addition, cigarette smoke and proteinases may both work to impair lung elastin resynthesis in the animal model of elastase-induced emphysema (38). Cigarette smoke also recruits inflammatory cells. In AAT deficiency, more neutrophils are found within air spaces than in emphysematous lungs of individuals with normal AAT plasma levels. This contributes to a greater NE load (39). This phenomenon might be attributable to the presence of neutrophil chemotactic factors, mainly leukotriene B4 released from alveolar macrophages (40). In addition, neutrophils and macrophages may release a variety of metalloproteinases with the potential to degrade extracellular matrix components (41). A role for a human collagenase in alveolar injury in experimental emphysema has also been demonstrated (42). Metalloproteinases are not inhibited by AAT and may even inactivate it by limited proteolysis near the active site (41). The C-terminal fragments of AAT released during proteolytic inactivation are potent neutrophil chemotactic factors (43, 44). LABORATORY TESTS
Observation of a reduced or absent
Quantitative Tests Plasma AAT levels are usually determined by rocket immunoelectrophoresis, radial immunodiffusion, or, more recently, by nephelometry. Commercially available standards, especially those used for radial immunodiffusion, tend to overestimate the AAT concentration by as much as 35–40% (45). To discriminate between historic values obtained using the nonpurified standard and those obtained with the pure standard developed by the U.S. National Institutes of Health, the former are expressed as milligrams per deciliter (mg/dl), and the latter in micromolar units (µmol/L or µM). The two units are, however, often used interchangeably in many continental European countries, irrespective of the standard used. Moreover, nephelometry may also overestimate AAT levels, because of interference with lipids or hemoglobin. Also to be considered is that AAT is an acute-phase reactant, and inflammatory conditions may augment the steady state plasma AAT levels in Z heterozygotes. It should be noted that a "protective" threshold level of 11 µmol/L previously maintained corresponds to 80 mg/dl if measured by radial immunodiffusion and to 50 mg/dl if measured by nephelometry (see Table 4) . This protective threshold has evolved from the observation that patients with heterozygote phenotypes whose levels of AAT exceed this level are usually free from emphysema (29).
Qualitative Tests The most widely used method for identifying AAT variants is their separation based on the isoelectric point by means of thin-layer isoelectric focusing (IEF). This technique, commonly referred to as "phenotyping," requires skill and experience and should be performed in reference laboratories. The IEF specificity may be further enhanced by coupling it with an immunoblot or by using an immobilized pH gradient IEF gel (46). Phenotyping may be performed on serum or plasma samples. Some laboratories perform IEF on "dried blot spot" samples, using a blood drop absorbed on special paper, allowing for easier transport of samples. This method is suitable for screening purposes, but the identification of a deficient variant should be confirmed on serum or plasma samples. Diagnosis at a molecular level ("genotyping") is performed on genomic DNA, extracted from circulating mononuclear blood cells. Known mutations may be detected by allele-specific amplification or analysis. Lack of recognition of a known mutation may imply the presence of a new variant. In this case, a gene scan should be performed by means of direct sequencing, or denaturing gradient gel electrophoresis (47). Molecular level diagnosis has been made easier by the commercial availability of test kits capable of detecting S and Z alleles in whole blood or mouthwash samples. However, available kits will miss null alleles and plasma levels of AAT may also be necessary. IDENTIFICATION OF INDIVIDUALS WITH AAT DEFICIENCY
Early Detection: Prenatal There is no routinely available method developed for the prenatal diagnosis of the condition. Amniocentesis or chorionic villus sampling (48, 49) provides the material on which genetic testing can be performed. Requests for prenatal diagnosis may be based on a history of perinatal liver disease in a previous sibling, in which case the risk of developing liver disease may rise substantially (9, 50). Several techniques of prenatal gene identification have been reported and are available in limited cases. All require techniques of DNA amplification and use specific probes to provide adequately specific diagnostics (51, 52). However, financial and practical considerations limit their usefulness. Postnatal detection of AAT deficiency depends on a high level of suspicion. The technology for rapid screening techniques is available and utilizes DNA amplification from heel blood samples (53). Postnatal detection may occur in the setting of neonatal hepatitis or a strong family history. Otherwise, most cases remain undetected unless emphysema, liver disease, or rare complications develop. Although AAT deficiency is one of the most common codominant disorders to affect Caucasians, routine screening is not performed.
Detection in Adults Three categories of genetic testing have been specified (see the GENETICS, PSYCHOSOCIAL, ETHICS, AND ECONOMIC ISSUES section). The first type is labeled "diagnostic" testing and refers to the testing of individuals with symptoms and/or signs consistent with an AAT deficiency-related disease. The second type of testing is labeled "predispositional" testing, which refers to identifying asymptomatic individuals who may be at high risk of having AAT deficiency. The third type of testing is labeled "screening," which refers to programs designed to search in populations for persons possessing certain inherited predispositions to disease. The hallmark of screening is that there should be no previous suspicion that any given individual has the condition being tested. Specific recommendations and associated recommendation grades for testing in specific groups of individuals are given in Table 8 of the GENETICS, PSYCHOSOCIAL, ETHICS, AND ECONOMIC ISSUES section. Subjects with abnormal blood levels should be investigated further to provide a qualitative evaluation of their AAT disorder. Even subjects with a borderline normal AAT plasma level (12–35 µmol/L or 90–140 mg/dl) and their first-degree relatives should undergo qualitative testing, because these levels may correspond to an intermediate level phenotype (SZ, SS, MZ) and a relative with asymptomatic or misdiagnosed AAT deficiency may be uncovered within the family.
Beside occasional observation of a reduced or absent
PATHOLOGY At autopsy, panacinar emphysema with basal predominance is seen in all adult patients with severe AAT deficiency (56). Even in an 11-year-old girl who died from intraabdominal hemorrhage due to cirrhosis, uniform panacinar emphysema was found at autopsy (57). On occasion, minimal centrilobular emphysema is observed in the upper lobes. In 2 of 14 autopsies, where descriptions from inflation-fixed specimens are available, cylindrical bronchiectasis has been reported (56). Descriptions of bronchiolar and bronchial histology in individuals with AAT deficiency are sparse in the literature. The Reid Index, reflecting bronchial gland hypertrophy, was reported as normal in one case, with mild gland enlargement noted in another case. Also, loss of muscle and elastic fibers in small bronchi was noted. In lung tissue resected from patients with severe emphysema due to AAT deficiency and undergoing lung volume reduction surgery, changes at the level of bronchioli (bronchiolitis obliterans, bronchiolectasia, acute and chronic bronchiolitis, bronchiolitis with organizing pneumonia) were more frequently observed compared with emphysema patients without AAT deficiency (58). On occasion, large bullae, preferentially in the basal parts of the lungs, are described at autopsy, in surgical specimens, or as seen by X-ray. SYMPTOMS (See Appendix 1 Symptomatic obstructive lung disease in AAT deficiency usually presents at a mean age between 32 and 41 years in individuals with a history of smoking (6, 59–63). Considerable variability in the time of onset of symptoms has been described, but symptoms rarely present before age 25 years. Although severe symptoms are most often seen in current or previous cigarette smokers, some smokers and many nonsmokers develop no symptoms at all (64, 65). The largest cohort of patients (n = 1,129) queried with a standardized symptom questionnaire (66) were participants in the National Heart, Lung, and Blood Institute (NHLBI) Registry of Individuals with Severe Deficiency of AAT (67). This registry included individuals with an AAT serum level < 11 µM and included some subjects ascertained through family screening (20%), often in the absence of symptoms. The most frequent symptom elicited was dyspnea on exertion (in 84% of participants). Self-reported wheezing during respiratory tract infections was prominent (76%), although wheezing independent of infections was also common (65%). A cough was usually present in 42% of participants in the NHLBI Registry. Increased cough and phlegm for at least 3 weeks in a year were described by 50% of individuals (67) and may present as early as age 18 years (68). Other studies have described a chronic productive cough for 3 months in at least two successive years, consistent with chronic bronchitis in 8–40% of AAT-deficient patients (68–70). A chronic cough with or without sputum production has been seen in association with radiographic features of cylindrical bronchiectasis (70). The presence of episodic wheezing and dyspnea consistent with a diagnosis of asthma has been noted in AAT deficiency. In a study evaluating the presence of wheezing, bronchodilator responsiveness, atopy, and increased serum IgE, three or more of these markers for asthma were found in 22% of AAT-deficient patients compared with 5% of COPD patients without AAT deficiency (69). Allergic rhinitis was common even when airway obstruction was not present. In the NHLBI Registry, 35% of participants self-reported a history of asthma and more than 50% demonstrated a significant postbronchodilator reversal of airflow obstruction (more than 12% and 200 ml) on serial testing (67, 69). In this registry, the mean age at which the first symptom, wheezing, manifested itself was 31 years. No study of a population-based cohort has adequately addressed the prevalence of catastrophic disease in AAT deficiency. The best data available come from the NHLBI Registry (67), in which a majority (72%) of deaths were due to emphysema. A chest illness in the past 3 years that kept the patient off work, indoors at home, or in bed was self-reported by 68% of patients. Thirty percent of NHLBI Registry participants reported medical disability at a mean age of 46 years, indicating the significant morbidity associated with AAT deficiency (67). In summary, the respiratory symptoms of patients with AAT deficiency are striking in their early age of onset. PHYSICAL FINDINGS No physical finding is sensitive or specific enough to be clinically useful in detecting the AAT-deficient individual. Wheezing is common; yet, the absence of wheeze on examination can occur in severe emphysema. Progressive disease is associated with signs of chest hyperinflation, reduced breath sounds at the bases, and muscle wasting. Because the most common alternative misdiagnosis is asthma, spirometry should supplant physical findings in patient evaluation; spirometric measures should return to normal in most patients with adequately treated asthma. LUNG FUNCTION TESTS Pulmonary function testing should include spirometry (pre- and postbronchodilator), lung volume measurements by helium dilution or by body plethysmography, and single-breath CO-diffusing capacity (71, 72). Spirometry is the pulmonary function test that is most often performed in AAT-deficient individuals because it is reproducible and reflects an important aspect of the lung disease. The spirometric abnormalities include reduction in the forced expiratory volume in 1 second (FEV1) and a normal or reduced forced vital capacity (FVC). The obstructive impairment (reduced FEV1/FVC ratio) is primarily due to loss of elastic recoil from parenchymal disease (emphysema) with dynamic collapse of otherwise normal airways. The flow–volume curves usually show a marked decrease in flow with decreasing lung volumes, typically evidenced by concavity of the expiratory portion of the flow curve. The reduced elastic recoil results in increased lung compliance, which allows for hyperinflation with increases in residual volume (RV) and total lung capacity (TLC). Due to areas of lung that are poorly ventilated (air trapping), static lung volumes measured by body plethysmography are usually greater than those measured by dilution of an indicator gas. Emphysema of the lung parenchyma also impairs gas exchange with reduction in the diffusing capacity and a widening of the alveolar–arterial gradient for oxygen. Although they are often different aspects of the same pathological process (emphysema), reduction in expiratory flow (FEV1) and reduction in the diffusing capacity are not always well correlated (73, 74), and both should be determined when assessing the overall severity of pulmonary impairment in AAT-deficient individuals. In addition, arterial oxygen tension adds information about disturbed ventilation–perfusion relationships. In more advanced pulmonary disease, the effect of emphysema on muscle activity of the thorax and diaphragm muscles can be assessed by measuring maximal inspiratory and expiratory mouth pressure. Predictive values have been published (75). The cardiopulmonary status can also be assessed by exercise testing. While in normal individuals the PaO2 may not change, or even increase, on exercise, AAT-deficient individuals may show markedly decreased PaO2 and an increased alveolar–arterial oxygen difference. Individuals with AAT deficiency have increased respiratory rates at rest, and on mild exercise rapidly reach more than 80% of their predicted maximal voluntary ventilation, indicating that ventilation may become a limiting factor at higher work levels (76). Although symptoms suggesting airway hyperresponsiveness such as cough and wheezing are present in an appreciable proportion of AAT-deficient individuals and some are initially diagnosed as having asthma, the reversibility in airflow obstruction after an aerosol bronchodilator is usually moderate (69).
Conclusions Because AAT-deficient individuals mainly develop fixed airflow obstruction, it does not seem justified to assess variability of airflow obstruction by peak expiratory flow monitoring in most subjects with AAT deficiency. However, follow-up of patients should include spirometry at yearly intervals. RADIOLOGY, INCLUDING COMPUTED TOMOGRAPHY AND VENTILATION–PERFUSION SCAN
Emphysema Computed tomography is much more sensitive than plain chest radiography or pulmonary function tests for the presence of emphysema (74, 83, 84). High spatial frequency reconstruction of images (high-resolution computed tomography [HRCT]) is more sensitive for detecting morphologic changes such as bullous disease and bronchiectasis. On HRCT, emphysema is characterized by the presence of areas of abnormally low attenuation, which can be contrasted with surrounding normal lung parenchyma if a sufficiently low window level (–600 to –800 Hounsfield units [HU]) is used. In AAT deficiency, the classic finding is panacinar emphysema in terms of uniform abnormally low attenuation of lobules, and predominant lower lobe distribution. Pulmonary vessels in the affected lung appear fewer and smaller than normal (85), but mild and even moderately severe panacinar emphysema can be subtle and difficult to detect radiographically (86). Whereas focal areas of emphysema usually lack distinct walls, bullae, by definition are sharply demarcated by a thin wall and measure 1 cm or more in diameter. Bullae are more common in usual (non-AAT deficiency) emphysema (79).
Bronchiectasis
Lung Density Evaluation Ventilation–perfusion scanning may be a useful tool in detection of early changes associated with AAT deficiency, as even individuals with relatively normal lung function may have abnormal scans (63, 76, 92–95). Typically, the ventilation scan shows symmetric distribution of xenon-133 throughout all zones of the lung during the equilibrium phase followed by a symmetric delay in washout, most prominent in the lung bases and midzones. A symmetric loss of pulmonary arterial perfusion is also found, most marked in the bases. In summary, a chest X-ray should be performed as an initial test for incidental lung lesions or possible identification of localized bullous disease. However, CT scanning, including thin slices for morphology and thick slices for densitometry, is presently the most definitive technique to detect and quantify the presence of emphysema in AAT deficiency. PARAMETERS OF PROGRESSION: FEV1, DESMOSINE, AND COMPUTED TOMOGRAPHY The standard method for monitoring the progress of emphysema is by pulmonary function tests, and rate of decline of FEV1 is by far the most commonly used measurement in longitudinal studies. However, spirometry has shortcomings in assessing patients with emphysema. Because airway obstruction is due mainly to dynamic collapse, the results of spirometry are heavily dependent on the cooperation and effort of the individual. Slow vital capacity is usually greater than FVC and, similarly, the FEV1 can be greater with a submaximal than with a maximal effort. It is an advantage of spirometry that it is simple to perform and can be easily repeated frequently. However, it has been shown that frequent measurements less than 3 to 6 months apart are not worthwhile, because measurements at short intervals will add little extra information to measured changes over the longer term (96). FEV1 is considered to be quite reproducible. In several large multicenter studies (97), spirometry of high technical quality, performed on separate days, had a standard deviation of about 100 ml. However, this measurement error is large in comparison with the annual decline in FEV1, which in normal adults is about 30 ml and in AAT-deficient individuals is about 60 ml. The measurement error implies a standard error of at least 100 ml/year when estimating the slope of decline in FEV1 in individual subjects who have been monitored for no more than 1 year. The standard error is inversely proportional to the observation period (i.e., with an observation period of 10 years, the standard error of the slope reduces to 10 ml/year, which is still quite large). The variability of repeated measurements of the single-breath diffusing capacity is greater than the variability of FEV1 measurements, and therefore the diffusing capacity has less potential as a progression parameter. Although blood gas composition and diffusing capacity for carbon monoxide are frequently measured in the course of managing patients with AAT deficiency, studies have not been published demonstrating their effectiveness as follow-up parameters. From a conceptual point of view, densitometric parameters derived from repeated CT scans could be sensitive and specific markers of the emphysematous process, and as Flenley suggested more than a decade ago, the progression of emphysema may be assessed more accurately by repeated quantitative CT than by measuring the FEV1 (98, 99).
Radiology The belief of some investigators that spirometric control of ventilation during scanning improves the reproducibility and accuracy of density measurements (106–108) has been complicated by the recognition that patients with COPD are less able to successively reproduce levels of full expiration and inspiration to allow standardization (109, 110). Analysis of repeated CT scans at various levels of inspiration has revealed the relationship within an individual between lung density and volume. On the basis of this relationship, densitometric parameters can be standardized by log-transformed lung volume, which corrects for differences in lung volume between scans and eliminates the need for spirometrically controlled CT (111). Using a broad range of pixel percentiles from the 10th to the 30th (corresponding to densities ranging from –950 to –890 HU), the annual decline was found to be 2 HU, corresponding to a loss of lung tissue of 2 g/L lung volume (111). CT quantitation of emphysema by densitometric parameters seems to be a more sensitive measure of the progress of emphysema as compared with pulmonary function tests (e.g., FEV1) (98, 112, 113). Inspiratory CT was superior to expiratory CT for longitudinal estimation of structural abnormalities caused by aging and smoking (113) and the pixel percentile was more robust than the pixel index for monitoring the progress of emphysema (111). In a randomized clinical trial of AAT augmentation therapy over a period of 3 years with 56 patients, the sensitivity to measure the progression of emphysema by the percentile method proved two- to threefold higher than any parameter measured by spirometry or CO-diffusing capacity. This implies that new drug trials using CT as any outcome parameters are feasible with a fivefold lower number of patients (112). Because it has been shown that CT lung density is influenced by age, normal CT attenuation values for the lung by age should be established (101, 113–116). Furthermore, pixel attenuation values fluctuate with the position in the thorax and change with aging of the X-ray tube (117). A problem related to the use of CT for monitoring the progress of emphysema is radiation exposure. Limiting the examination to a single slice 5 cm below the carina would markedly reduce the radiation dose and results derived from calculations based on a thin slice were similar to results based on a volume scan of the whole lung (111). Also, a reduction of the electrical current (mA) to levels 10 times below standard settings has little influence on lung density measurements (118, 119).
Biochemical Markers DES and IDES are cross-linked amino acids unique to mature elastin that are contained in elastin-derived peptides in the bloodstream and excreted in urine. Urinary DES levels are higher in smokers with a rapid decline of lung function indices than in those with slow decline (125). In addition, they are as high in subjects with AAT deficiency as in subjects with usual, AAT-replete COPD (123). Preliminary evidence that AAT augmentation therapy decreases urinary DES excretion in AAT-deficient subjects (126) prompted investigators to design clinical trials of short-term supplementation therapy with the primary end point being reduction of the urinary rate of excretion of DES/IDES. Results of one of these trials could not confirm the preliminary finding (127). Taken together, studies thus far support urinary DES/IDES as potential candidates for monitoring progression of lung disease and efficacy of therapy in AAT-deficient subjects, but further evidence is needed to demonstrate methodologic reliability and clinical relevance to progression. In summary, there are adequate data to suggest that FEV1 and CT densitometry are reliable methods to detect progression of emphysema in AAT deficiency. Spirometry should initially be performed on an annual basis until it is clear that progression is not rapid when a reduction in frequency of assessment can be initiated. RISK FACTORS A number of studies have demonstrated the role of various risk factors for the development of COPD in patients who have the PI*ZZ phenotype (see Table 6 and Appendices 3 and 4). It is clear that smoking is the most important risk factor for the development of emphysema in AAT deficiency of the PI*ZZ type. The annual decline of FEV1 in smokers with AAT deficiency is about 130 ml, and 70 ml in ex-smokers (67, 128–130). However, a later series (131) has shown mean declines of 70 ml/year in current smokers, 47 ml/year in never-smokers, and 41 ml/year in ex-smokers, indicating similar decline rate in nonsmokers and ex-smokers. To study other environmental and intrinsic factors contributing to the decline in lung function, nonsmoking status of participants must be assured to avoid the confounding effects of active smoking. In Sweden, Denmark, and the North American registries, large numbers of patients are available for follow-up studies.
Three reports have addressed the issue of impact of environmental factors on lung function decline based on self-reported exposures. In a series of 225 nonsmoking PI*ZZ individuals in Sweden with an FEV1 of 84 ± 28% predicted (mean ± SD), the history of occupational exposure for at least 3 months to gas, fumes, or dust; the frequency of annual colds; and the number of attacks of pneumonia were analyzed as possible risk factors in lung function (132). Increasing age, male sex, and symptoms of wheezing were identified as independent determinants of FEV1 decline. Among men over 50 years old, wheeziness and occupational exposure to airway irritants were independent determinants of lung function. A subsequent report concerning the same patients showed that self-reported passive smoking had increased risk for chronic bronchitis and that the use of kerosene heaters and employment for more than 10 years in an agricultural environment were independent correlates of decreased lung function (133). With respect to passive smoking, other studies have also demonstrated a detrimental association with pulmonary symptoms (34, 68). A prospective study of 103 Swedish children with AAT deficiency detected at birth showed that they had normal lung function when they reached adulthood, indicating that childhood respiratory infections are not a major factor for development of emphysema (134). In a Danish study on never-smoking nonindex cases of PI*ZZ, no abnormalities in lung function could be identified (135). In addition to the Swedish studies, Seersholm and Kok-Jensen described 27 index cases and 48 nonindex cases and could not find an effect of passive smoking on the development of emphysema (136). Further analysis of the data from the Danish AAT Deficiency Registry showed that the beneficial effect of smoking cessation was due to a decreased decline in FEV1 among the quitters (128). The mean overall decline in FEV1 was 81 ml/year with a decline of 132 ml/year among the smokers, 58 ml/year in the group of patients who quit smoking during the study period, and 86 ml/year in never-smokers. It was also found that the rate of decline according to initial FEV1% predicted was U-shaped, with the most rapid decline in the group of patients with an initial FEV1% predicted between 30 and 64%. The North American NHLBI Registry monitored 1,129 patients with severe AAT deficiency for 3.5 to 7 years (137). The mean FEV1 decline was 54 ml/year, with more rapid decline in males, those aged 30–44 years, current smokers, those with FEV1 35 to 79% predicted, and those who ever had a bronchodilator response. In one report, Mayer and coworkers (138) studied 128 individuals with AAT deficiency of the PI*ZZ phenotype to examine the relationship between chronic respiratory symptoms, airflow limitation, treatment requirements, and semiquantitative estimates of occupational exposure to dust fumes, smoke, and gas. Increased prevalence of chronic cough and having left a job because of breathlessness were seen in individuals with high mineral dust exposure compared with individuals with no exposure. Subjects with high mineral dust exposure had a significantly lower FEV1 (31% predicted) compared with individuals with no exposure (40% predicted). Personal tobacco use was a significant risk factor for most outcome measures but no interaction with occupational exposure was seen. In summary, besides active cigarette smoking, a history of wheezing and some specific environmental exposures such as indoor kerosene heating and agricultural occupation accelerate the development of emphysema in male subjects over 50 years of age. Also, occupational inhalational exposures are independently associated with respiratory symptoms and airflow limitation. The weight of evidence also indicates that exposure to passive smoking is detrimental (34, 68, 133). NATURAL HISTORY Of 200,000 children screened in Sweden, 127 had the PI*ZZ phenotype and have been monitored prospectively since birth, both clinically and with liver and lung function measurements. During the first two decades of life, lung function remained normal in the Swedish cohort (139). Studies of the natural history of AAT deficiency have indicated that emphysema leading to early death usually begins in the third and fourth decades of life. In a study of life expectancy of 246 subjects by Larsson, the median age at death for smokers was estimated to be about 40 years and 65 years for never-smokers (6). A study of a referral population of 124 AAT-deficient patients by Brantly and coworkers showed a cumulative probability of survival to age 50 years of 52% and only a 16% chance of surviving to 60 years of age (63). However, both studies were based on patients selected from hospital records identified because of pulmonary symptoms and, to a certain degree, the estimate of life expectancy was probably too pessimistic because of selection bias. Data from the Danish Registry (140), from which 347 patients were included, indicated that FEV1 was the most important predictor of survival. Median survival for patients with FEV1 less than 25% predicted was 6.3 years, which increased to 10.5 and 14.2 years for those with FEV1 above 25 and 50% predicted, respectively. Tobin and coworkers studied the clinical course and survival of 166 patients with AAT deficiency, of whom 40 were nonindex cases, that is, ascertained through family studies (141). A much lesser degree of pulmonary symptoms was found in the nonindex group than in the index group and, in the nonindex group, none died compared with 23 in the index group. The study suggests a highly variable clinical course of the disease that cannot be explained only by differences in smoking history. In studying pulmonary function in 22 index cases and 30 nonindex cases, Silverman and coworkers also found large variations in pulmonary function between the two groups, and some subjects in the nonindex group did not have any pulmonary symptoms at all (34). It was concluded that other familial factors might contribute to a severe clinical course. To obtain further insight into the natural history of AAT deficiency with particular focus on the nonindex cases, the Danish AAT Deficiency Registry was initiated in 1978 (54). Patients with AAT deficiency are reported by all Danish physicians, a family record is obtained, and family members are PI typed. By December 1998, the registry contained 695 subjects with AAT deficiency PI type ZZ or Z-null, of whom more than 200 were identified by family studies. With the data in this registry, it has been possible not only to repeat the analysis of life expectancy conducted by Larsson in 1978 (6), but also to analyze the life expectancy of a large number of nonindex patients who did not have pulmonary symptoms (54). The nonindex smoking patients had a median life expectancy of 49 years whereas the median life expectancy of nonsmoking patients was 69 years, not statistically significantly different from that of the normal Danish population. Further analysis of the data with control for lifetime tobacco consumption showed that the difference in life expectancy between index cases and nonindex cases could not be explained by differences in smoking history only, and some smokers never develop severe emphysema (54). Risk factors other than smoking could be genetic or environmental factors such as exposure to dust and fumes, frequent pulmonary infections, or asthma (34, 68, 142–144). The possibility that bronchial hyperresponsiveness may increase FEV1 loss over time has been incompletely explored in AAT deficiency (137). The most obvious approach would be to study the clinical course and prognosis of never-smokers with AAT deficiency, but only a few such studies exist, and they have a limited number of patients and follow-up time. In a Swedish study of 225 self-reported never-smoking PI*ZZ individuals, most have normal lung function until 50 years of age, and only a few of them were identified because of respiratory symptoms. Above 50 years of age, there were great differences in lung function between individuals, and the mean values (expressed as a percentage of predicted normal) declined significa |
35% predicted) or mild (e.g., FEV1 
50–60% predicted) airflow obstruction are less clear. 
