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Published ahead of print on April 14, 2003, doi:10.1165/rcmb.2002-0271OC
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American Journal of Respiratory Cell and Molecular Biology. Vol. 29, pp. 390-396, 2003
© 2003 American Thoracic Society
DOI: 10.1165/rcmb.2002-0271OC

{alpha}1-Antitrypsin Deficiency Alleles in Cystic Fibrosis Lung Disease

Despina D. Frangolias, Jian Ruan, Pearce J. Wilcox, A. George F. Davidson, Lawrence T. K. Wong, Yves Berthiaume, Rosamund Hennessey, Andreas Freitag, Linda Pedder, Mary Corey, Neil Sweezey, Julian Zielenski, Elizabeth Tullis and Andrew J. Sandford

McDonald Research Laboratories/iCAPTURE Centre, and Division of Biochemical Diseases, Department of Pediatrics, University of British Columbia, B.C. Children's Hospital, Vancouver, British Columbia; Department of Medicine, Universite de Montreal and Centre de Recherche Hotel-Dieu du Chum, Montreal, Quebec; McMaster University & Hamilton Health Sciences Corp., Hamilton; and Hospital for Sick Children, and St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada

Address correspondence to: Despina Daisy Frangolias, McDonald Research Laboratories/iCAPTURE Centre, University of British Columbia, St. Paul's Hospital, 1081 Burrard Street, Room 292, Vancouver, BC, V6Z 1Y6 Canada. E-mail: Dfrangolias{at}mrl.ubc.ca


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) genotype does not explain the heterogeneity observed in CF pulmonary disease severity. Modifier genes are implicated for this heterogeneity. {alpha}1-antitrypsin ({alpha}1-AT) is one of the few antiproteases capable of inactivating neutrophil elastase. We investigated whether {alpha}1-AT alleles (Z, S deficiency alleles and the 3' G1237->A mutation) were associated with increased disease severity and the {alpha}1-AT acute phase response during pulmonary exacerbations. This was a multicenter Canadian study. Seven hundred sixteen patients with CF (age range, 5.0–63.6 yr) were genotyped for the Z, S, and G1237->A polymorphisms of the {alpha}1-AT gene. Stable and acute levels of {alpha}1-AT were measured on 31 adult patients with CF and were correlated to clinical parameters. There were 69, 13, and 18 patients with CF who were MS, SS, and MZ, respectively. There were 95 and 7 patients with CF heterozygous or homozygous for the A1237 allele, respectively. {alpha}1-AT genotype did not predict pulmonary disease severity, and was not associated with more severe clinical outcome (death or lung transplantation) or age of onset of Pseudomonas aeruginosa infection. Body mass index was a significant predictor of {alpha}1-AT levels during exacerbations. {alpha}1-AT genotype is not a major contributor to the variability of pulmonary disease severity in CF.

Abbreviations: {alpha}1-antitrypsin, {alpha}1-AT • analysis of variance, ANOVA • bronchoalveolar lavage fluid, BALF • body mass index, BMI • cystic fibrosis, CF • cystic fibrosis transmembrane conductance regulator, CFTR • chronic obstructive pulmonary disease, COPD • forced expiratory volume in 1 s, FEV1 • forced vital capacity, FVC • neutrophil elastase, NE • polymerase chain reaction, PCR • percent of predicted FEV1, %predFEV1 • percent of predicted FVC, %predFVC • Schwachman-Kulczycki, S-K


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
The primary pathophysiologic processes responsible for premature death and disability in patients with cystic fibrosis (CF) are chronic pulmonary infection and inflammation. The inflammatory process in response to pulmonary infection in CF airways is characterized by a massive influx of neutrophils (1). Neutrophils represent less than 5% of the cells recovered in bronchoalveolar lavage fluid (BALF) in normal individuals, but in adults and children (1–5 yr of age) with CF, neutrophils may comprise up to 95% of the cell population (2). Neutrophils contain a number of proteolytic enzymes, one of which, neutrophil elastase (NE), has been implicated in excessive pulmonary damage observed in cigarette smokers and in patients with CF. Elevated levels of NE have been reported in the sputum of patients who have CF (3, 4). NE is capable of causing direct lung damage by hydrolyzing all the major connective tissue proteins that make up the lung and airway matrix. In additition, excess NE adversely affects the airways in CF, by enhancing mucus secretion (5, 6), and by interfering with the opsonization and elimination of bacterial pathogens, particularly Pseudomonas aeruginosa (5, 7). In normal hosts, the actions of NE are prevented primarily by {alpha}1-antitrypsin ({alpha}1-AT), a serine protease inhibitor that binds to NE and inhibits the breakdown of elastic tissue in the lung. Normal to elevated levels of {alpha}1-AT have been reported in airway secretions (2) and plasma (2, 8) in patients who have CF. Elevated levels of {alpha}1-AT have been reported during pulmonary infections in this patient population (9).

The extremely high levels of NE in the airways of CF patients clearly indicate that there is an imbalance between {alpha}1-AT and elastase in the airways of patients with CF. Since great variation in disease severity and progression exists among CF patients possessing the same cystic fibrosis transmembrane conductance regulator (CFTR) genotypes (10, 11) it is possible that genes other than the CFTR may contribute to pulmonary disease progression. If this were the case, individuals who have lower than normal levels of {alpha}1-AT may be at increased risk for lung damage. Several mutations of the {alpha}1-AT gene result in a deficiency of this antiprotease. There is also evidence that {alpha}1-AT genotype influences the acute phase response (12). Findings to date are inconclusive concerning the role that {alpha}1-AT may play in pulmonary disease progression in CF. Initial studies have been inconclusive (13–16), their main limitation being their small sample sizes and therefore the high possibility of type 2 error (false negative). The purpose of this study was twofold. First, to investigate whether the {alpha}1-AT gene (the Z, S deficiency alleles and the 3' G1237->A mutation) is a modifier of pulmonary disease progression in a large cohort of patients with CF who were characterized by a heterogeneous severity of pulmonary disease. Our main hypothesis was that heterozygosity for the Z and S alleles of {alpha}1-AT would result in earlier onset of pulmonary disease, more rapid deterioration in pulmonary function, and consequently more severe pulmonary dysfunction after controlling for other known predictors of pulmonary function decline. The second purpose of the study was to measure {alpha}1-AT levels at stable clinical status and acute increases during pulmonary exacerbations in an adult group of patients with CF who had varying degrees of pulmonary dysfunction. The rationale was to characterize the acute phase response to pulmonary infection in this patient group to help tailor the possible administration of antiproteolytic therapeutic agents.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Study Subjects
Out of a potential 1,220 patients, 716 patients volunteered for the study and clinical data were available on 714. The study cohort consisted of 250 patients who were 18 yr of age or younger (mean age [± SEM] 11.1 [0.2] and range 5.0–7.7 yr; male/female = 128/122) and 464 patients who were over 18 yr of age (mean age [± SEM] 29.2 [0.4] and range 18.1–63.4 yr; male/female = 247/216). Patients with a diagnosis of CF on the basis of clinical signs, elevated sweat chloride values, and/or positive genotyping for the CFTR gene were recruited for the study. Patients with CF who had received a lung transplant were also recruited and pulmonary function data for these individuals were collected before transplantation.

Patients attending the following Canadian CF clinics were recruited: Adult CF clinic at St. Paul's Hospital (n = 97) and Children's CF clinic at B.C. Children's Hospital (n = 97) (Vancouver, BC, Canada), Adult and Children's CF clinics at Hamilton Health Sciences (n = 47 and 37, respectively) (Hamilton, ON, Canada), Adult CF clinic at Hôtel-Dieu du Chum (n = 149) (Montreal, PQ, Canada), Children's CF Clinic at Hospital for Sick Children (n = 106) and Adult CF clinic at St. Michael's Hospital (n = 181) (Toronto, ON, Canada). An attempt was made to recruit all patients attending the participating clinics. Out of a potential 1,220 patients, 716 patients volunteered for the study and clinical data were available on 714, of which 250 patients were 18 yr of age or younger.

We also recruited 31 consecutive patients from the St. Paul's Hospital adult CF clinic (mean age [± SEM] 27.5 [1.1] years), who developed an acute pulmonary exacerbation to measure {alpha}1-AT levels during the acute phase and 2–3 mo later during a stable phase. Details of the experimental procedures and risks involved were explained to subjects before obtaining written consent, which was approved by the Ethics Committees of the institutions in this study.

Genotyping
DNA was extracted from blood leukocytes in 10 ml blood. Patients were genotyped for three {alpha}1-AT polymorphisms: the S and Z mutations in exons 3 and 5, respectively, and the TaqI polymorphism in the 3' untranslated region using polymerase chain reaction (PCR)-based restriction enzyme assays as described in the study by Sandford and associates (17).

Clinical and Laboratory Measurements
The subjects performed postbronchodilator spirometry (forced expiratory volume in one second [FEV1] and forced vital capacity [FVC]) in accordance with ATS criteria (18). A standard protocol was used by all centers. Values were expressed as a percent of the normal values based on age, sex, and height (19). The best-recorded postbronchodilator measurements were used for this study. Predicted values were calculated from the equations derived for adults (19) and children (20). For patients who had received lung transplantation, lung function data before transplantation were used for the regression model.

Pulmonary function data were obtained from the patients' medical charts, as was information on frequency and duration of pulmonary infections requiring intravenous antibiotic therapy for a 1-yr term. For these encounters, weight and sputum culture results were also recorded (infection with the following primary pathogens was recorded: P. aeruginosa and Burkholderia cepacia). Data were gathered during a period of stable clinical status. We collected dates to calculate age of CF diagnosis, age of first infection and when possible age of chronic infection with P. aeruginosa, infection with and age of chronic colonization with B. cepacia, age of transplantation, and death. We also created a categorical variable for chronic infection with P. aeruginosa to increase study sample size as in some cases it was not possible to obtain the age of first or chronic infection with this pathogen, but it was possible to categorize them as chronically infected or not. Additional phenotypes that were also collected were CFTR genotype, sweat chloride levels, pancreatic sufficiency, and presence of liver disease. Data were collected for the study cohort recruited for the interval from 1997 to June 2002.

Definition of Stable Clinical Status and Pulmonary Exacerbation in CF
Stable clinical status was defined as the absence of pulmonary exacerbation over previous 4 wk, absence of a current mild exacerbation requiring oral antibiotics, and the absence of two or more clinical symptoms (increased cough, sputum volume and purulence, increased dyspnea, reduced weight, and a fall in FEV1 > 10%). Pulmonary exacerbation was defined as a pulmonary infection that required the administration of intravenous antibiotics based on clinical signs assessed by the CF physician.

Measurement of {alpha}1-AT Levels during a Pulmonary Exacerbation Episode
Patients with CF with a history of liver disease, or liver/lung transplanted were excluded from the levels {alpha}1-AT levels sub-study. Patients from the St. Paul's Hospital CF clinic were recruited at the time of admission for an acute pulmonary exacerbation. These patients were characterized into two groups based on %predFEV1 during clinical stability: mild/moderate pulmonary impairment (%predFEV1 > 50% predicted), and severe pulmonary impairment (%predFEV1 <= 50% predicted). For this group we calculated Schwachman-Kulczycki (S-K) (21) and Brasfield (22) scores during clinical stability. We also obtained from the patients' medical charts the number of days treated for pulmonary infections over a 2-yr period (number of hospitalization days).

Blood samples for measurement of {alpha}1-AT were obtained within the first two days of hospital admission and repeated at Days 4, 7, 10, and 13 of a 14-d therapeutic intervention for most patients. Stable {alpha}1-AT levels were measured 2–3 mo after exacerbation during clinical stability. These patients were also included in the larger study and were genotyped for the {alpha}1-AT polymorphisms.

Statistical Analysis
The primary outcome variable, depicting pulmonary disease severity was %predFEV1. A mixed effects linear regression model was used to model the effect of {alpha}1-AT genotype on %predFEV1. Parameters also used as independent variables in our equations were current age, sex (categorized as male [0], female [1]), age of CF diagnosis, CFTR genotype (categorized as homozygous {Delta}F508 and heterozygous {Delta}F508 or other, coded 1, 2, 3 respectively), pancreatic sufficiency status (categorized as insufficient [0] and sufficient [1]), body mass index (BMI) and infection with P. aeruginosa and center code. We used the variable labeled Center to assess overall if there was evidence of center-to-center variability. The analysis used was a mixed effects model using a random effect for center in the model. With this analysis the actual coding used has no significance; rather, we were determining whether or not there was evidence of center-to-center variability. Infection with P. aeruginosa was used as a categorical variable (P. aeruginosa [PA] status as infected [1] and not infected [0]) in the regression analysis. We defined acute phase increase in {alpha}1-AT (% change in {alpha}1-AT) as the difference between stable value and the value collected during the first 2 d of hospitalization for the exacerbation. Stepwise linear regression analysis was used to predict %change in {alpha}1-AT and parameters used included current age, sex, CF diagnosis age, CFTR genotype, pulmonary disease (%predFEV1, %predFVC, S-K clinical scores [21], Brasfield scores [22]), BMI, number of hospitalization days over 2 yr. Data analysis was performed using SPSS statistical software (SPSS statistical software, Chicago, IL) and Splus (Insightful Corporation, Seattle, WA).


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Tables 1 and 2 show demographic and clinical measures for our study cohort stratified by {alpha}1-AT genotype. Prevalences of the S, Z alleles were similar to expected frequencies (Z = 1–3% and S = 1–11%) in the normal population. Heterozygosity for the 3' G1237->A mutation has been documented from smaller studies to be 5–15% for heterozygosity for the A allele (17, 23). Figures 1A and 1B show %predFEV1 and sample size by {alpha}1-AT genotype. Z and S alleles of the {alpha}1-AT gene did not predict pulmonary disease severity, and were not included in the final regression equation (%predFEV1 = 70.1 + 0.76 x CF Diagnosis Age - 1.29 x Exam Age + 7.43 x Pancreatic sufficiency status + 0.71 x BMI, R2adj = 0.23, P = 0.0001). The effect of the variable Center was included as a random effect; however, center-to-center variability was small (less than 1% of the total variability). To determine whether inclusion of patients < 18 yr of age (who had less severe pulmonary disease) could reduce the power to detect a significant association with a genetic modifier, the analysis was repeated in the subset of patients > 18 yr of age. This analysis confirmed the lack of association of the Z and S alleles with disease severity seen in the entire group (AAT genotype continues to not be a significant predictor, P = 0.96). To determine whether there was a specific interaction of AAT genotype with {Delta}F508, which may have been obscured by the presence of other CFTR alleles, we also ran this model selecting only those who were homozygous {Delta}F508; however, {alpha}1-AT genotype was not a significant predictor.


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  		TABLE 1 Clinical characteristics of study subjects stratified by {alpha}1-AT S and Z genotypes

 

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  		TABLE 2 Clinical characteristics of study subjects stratified by {alpha}1-AT 3' G1237->A genotype

 



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  		Figure 1. (A) Pulmonary disease progression and Z and S alleles of the {alpha}1-AT gene. (B) Pulmonary disease progression and the 3' G1237->A mutation of the {alpha}1-AT gene.

 
In the second model we included the categorical variable P. aeruginosa infection status, available for 555 of the 714 study subjects. This model accounted for 25% of the variability in cross-sectional pulmonary disease severity (%pred FEV1 = 79.21 - 1.23 x Exam Age - 9.56 x PA infection status + 0.66 x CF Diagnosis Age + 0.50 x BMI, R2adj = 0.25, P = 0.0001). B. cepacia colonization status (i.e., not infected versus chronic infection with the pathogen) was available for 558 patients (from the Vancouver, Hamilton, and Toronto centers) and was evaluated as a predictor of pulmonary disease severity. This parameter was not a significant predictor of pulmonary disease in our cohort. The Toronto cohort did show higher prevalence of B. cepacia chronic infection (26% of their sample) compared with the Hamilton and Vancouver cohorts (9.5% and 10.2% of the study samples, respectively). Similar analyses were used to investigate the 3' G1237->A mutation in the {alpha}1-AT gene, and results showed that this mutation also did not predict pulmonary disease.

We did not show increased prevalence of death or lung transplantation in patients with CF who were homozygous or heterozygous for the Z, S or the 3' G1237->A alleles versus wild-type (Tables 1 and 2). Patients with CF who had died or who were lung transplant recipients were significantly older (mean [± SEM] = 28.6 [± 1.3] yr) than patients with CF who were still alive (21.3 [± 0.4] yr; P = 0.0001), although both groups had been diagnosed with CF at similar mean (± SEM) ages (3.7 [± 0.8] and 4.5 [± 0.3] yr, respectively, P = 0.44). We showed similar frequency of pulmonary exacerbations and duration of intravenous therapy (over 12 mo) in the {alpha}1-AT genotypic groups (Tables 1 and 2). B. cepacia colonization was not shown to be more prevalent in those patients with CF who were carriers of the Z, S, or 3' alleles (data not shown). Liver disease status was available for 553 of the study subjects. We did not show increased prevalence of the Z or S alleles in patients identified with liver disease (7 out of 76) compared with wild-type patients (45 out of 477; P = 0.58). Specifically, only 3 of the 16 patients heterozygous for the Z allele were identified with liver disease.

Table 3 shows the anthropometric, clinical, and lung function data as well as stable and acute phase increases in {alpha}1-AT levels in our sub-study group investigating {alpha}1-AT levels. As expected, there were significant differences between groups in measures of disease severity (i.e., %predFVC, S-K, and Brasfield scores). The stable status levels of {alpha}1-AT were within the normal range for the mild/moderate group and outside the upper limit of the normal range in our laboratory for the severe group (Figure 2). The peak values for {alpha}1-AT during pulmonary exacerbation were significantly elevated above normal in both groups, and declined at a similar rate throughout the 14-d intervention. Although the levels in patients with severe pulmonary disease were lower at most time points, neither group returned to normal in the 14-d period (Figure 2). The percent change in {alpha}1-AT levels from peak to stable was greatest in patients with mild/moderate pulmonary disease, whose mean value was within the upper limit of the normal range (0.95–1.77 g/L) at the time of stable status, whereas that of patients with severe pulmonary disease was not. Stepwise regression identified BMI as a predictor of percent change in {alpha}1-AT (% change in {alpha}1-AT = -50.5 + 3.5 x BMI; adjusted R2 = 0.08, P = 0.05).


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  		TABLE 3 Characteristics of the subgroup of patients in the acute phase {alpha}1-AT level study

 


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  		Figure 2. {alpha}1-antitrypsin levels during a pulmonary exacerbation and post-exacerbation levels during stable clinical status. Levels are shown during the intravenous antibiotic intervention period (14 d) and at a post-exacerbation (stable) time point by pulmonary disease severity. Dotted lines show the range of normal levels for {alpha}1-AT.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The results of this study indicate that the {alpha}1-AT gene is not a modifier gene in CF. In the large study group Z and S polymorphisms were not associated with increased pulmonary disease severity as defined by pulmonary function, frequency and duration of pulmonary exacerbations, death or lung transplantation. Similarly, the A allele of the 3' mutation in the {alpha}1-AT gene was not protective. We showed a blunted acute phase increase in {alpha}1-AT to pulmonary infection in those patients with CF in a malnourished state. As we recruited consecutive patients for the {alpha}1-AT levels study as they were admitted for a pulmonary exacerbation, it is conceivable that our cohort is biased toward patients with more severe CF who require more frequent intravenous antibiotic therapy. However, patients with mild pulmonary disease infrequently require admissions for pulmonary exacerbations and therefore such a bias is difficult to avoid.

The {alpha}1-AT MZ genotype has been shown to be a risk factor for chronic obstructive pulmonary disease (COPD) (24). In CF cohorts, the association of {alpha}1-AT genotype and pulmonary disease severity is unclear. Doring and colleagues (13) found no association between {alpha}1-AT S and Z alleles and pulmonary disease severity but they did show an earlier age of onset of P. aeruginosa infection in individuals with these deficiency alleles (6 out of a total sample of 215). Mahadeva and associates questioned this association and in fact showed that patients who were heterozygous for the S and Z alleles (19 out of a total sample of 147) had higher levels of pulmonary function than the wild-type individuals (15). In another study, the same authors showed that the {alpha}1-AT Z and S deficiency alleles were not more prevalent in those patients with CF with severe pulmonary disease (dead or lung-transplanted patients with CF) (14). We also showed no difference in outcome (death or transplant) for our cohort, but our cohort was followed prospectively for a relatively short time interval (5.5 yr).

Kalsheker and associates (23) showed that the 3' mutation was associated with COPD (23). Morgan and colleagues provided in vitro evidence that the association with COPD may be due to deficiency in the {alpha}1-AT acute phase response (12). However, we (17) did not find that the 3' mutation attenuated the acute phase rise in {alpha}1-AT as shown in our study of patients undergoing open-heart surgery. Similarly, Madadeva and coworkers showed that the 3' mutation had no effect on {alpha}1-AT levels in patients with CF (15). In a recent study by Henry and associates (16) they showed less severe pulmonary disease and fewer infective pulmonary exacerbations over 2 yr in patients with CF who were heterozygous for the A allele for the 3' mutation. These data suggest that heterozygotes may have a slower disease progression. Our study data (which also included seven homozygous individuals for the A allele) did not support the findings of Henry and associates (16). None of our measures of disease severity showed the A allele to be associated with less severe pulmonary disease.

In genetic association studies such as this, population stratification based on ethnicity can be a confounding factor. However, as expected the vast majority of our study sample was white, and therefore it is unlikely that the lack of association in this study represents a type 2 error due to stratification. In a multicenter study such as this, there may have been differences in ethnic diversity between centers. To address this, and other potential confounders, we created a categorical variable called "center." However, center was not a significant predictor of lung function, and center-to-center variability was small (< 1% of the total variability, which was less than the variability within centers). This result suggests that there were no large ethnic differences between centers that could have affected the association of genotype with measures of lung function.

Other possible confounders in our study include social class and environment (i.e., smoking/passive smoking, increased exposure to air pollutants, and infectious agents) and differences in center care, even though care across Canadian CF clinics is standardized. Because center was not a significant predictor of lung function, this suggests that these variables were also not confounding factors in our analysis.

Interestingly, infusions of {alpha}1-AT have been shown to reduce NE to undetectable levels in CF BALF (25). We showed that patients with CF with severe pulmonary disease (i.e., %predFEV1 < 50%) had a blunted acute phase rise in {alpha}1-AT. Also noted is a much lower percent change in {alpha}1-AT levels from peak to stable in patients with CF with severe disease. Possible reasons for this difference are the higher baseline values in the severe group and also the possibility of milder exacerbations in the severe group leading into hospitalization or initiation of home intravenous therapy compared with the mild/moderate group. Patients with CF with severe disease were also likely to show poor nutritional status, which has been shown in cohorts without CF to affect {alpha}1-AT levels. The mean 20% increase in {alpha}1-AT during an acute infection reflects a relatively small acute phase response. Voulgari and associates reported a 78% increase in {alpha}1-AT levels to bacterial infection in a population without CF (26). Kueppers measured {alpha}1-AT levels in response to a typhoid vaccine injection in otherwise healthy males who were homozygous wild type and heterozygous for the {alpha}1-AT deficiency alleles Z and S (27). Although there was a lower baseline {alpha}1-AT levels in heterozygotes, a similar percent rise in levels was seen across the groups. In the study by Kueppers (27), {alpha}1-AT levels were monitored over 15 d; both the homozygous wild type and heterozygotes for the deficiency alleles showed a gradual return to normal values, unlike the pattern seen in our group who had severe pulmonary disease. It may be that the blunted acute phase increase in {alpha}1-AT levels in our study is related to the chronic pulmonary bacterial infection in CF. Alternatively, poor dietary intake and malabsorption leading to malnutrition and cachexia could play a role. Morlese and associates measured the acute {alpha}1-AT phase response to infection in nine 10-yr-old children who were also diagnosed with severe malnutrition (28). These children showed a blunted acute phase increase in {alpha}1-AT to bacterial infection. Patients with CF who showed heterozygosity for the S and Z polymorphisms also showed BMI values indicative of malnutrition, as well as a significantly lower percent increase in {alpha}1-AT levels during pulmonary exacerbation. In our analyses BMI was an important predictor of {alpha}1-AT levels, even when the patients with CF who were heterozygous for the S and Z polymorphisms were selected out, suggesting that BMI irrespective of {alpha}1-AT genotype is a predictor of percent change in {alpha}1-AT levels during pulmonary exacerbation. Although we did not show significant differences for BMI when our cohort was grouped by pulmonary disease severity, the mean BMI for the severe group was below 20 kg/m2 (Table 3), indicative of poor nutritional status and malnutrition. All the Canadian clinics promote patients to maintain normal body weight (i.e., adult BMI values between 20 and 25 kg/m2, and preferably between 22 and 25 kg/m2) to allow for weight loss that usually occurs during periods of pulmonary exacerbation or other CF-related illnesses. It is likely that a combination of poor nutritional status and chronic pulmonary bacterial infection, which is common in patients with CF with severe pulmonary disease, contributes to the pattern shown in stable and acute rise in {alpha}1-AT levels observed.

In this study, we used the common lung function parameter %predFEV1 as a measure of disease severity. This parameter is universally used as a measure of pulmonary disease severity and also correlates with measures of nutritional status (i.e., BMI in adults and percent of ideal weight in children) and pancreatic sufficiency status. Clinical scoring using S-K and Brasfield chest radiographic scores are also used, but have not been commonly used in large-scale studies. A benefit of using S-K scores is that this score takes into account pulmonary, nutritional, chest radiographic status, and a measure of activity or mobility. Exercise capacity (29, 30), quality of life (31–33) and sputum volume (33), are alternative measures of pulmonary disease, but these measures are not commonly used in patients with CF in clinical assessment. As our study showed that nonpulmonary measures (i.e., BMI, PSS) affect pulmonary disease severity, this suggests that measures for multisystem CF disease severity such as BMI and PSS are essential.

The results of our study show that {alpha}1-AT genotype is not a major contributor to the variability of pulmonary disease severity in CF. Specifically, {alpha}1-AT genotype did not correlate with %predFEV1, pulmonary infections and death, or lung transplantation. Our study shows, however, that the levels of {alpha}1-AT during pulmonary infections may be affected by poor nutritional status independent of {alpha}1-AT genotype.


   Acknowledgments
 
This study was supported by a grant from Bayer/Red Cross. Dr. Sandford is a recipient of a Parker B. Francis Fellowship and holds a Canada Research Chair in Genetics. Ms. Frangolias is a recipient of a Canadian Cystic Fibrosis Foundation Studentship and a Michael Smith Foundation for Health Research Trainee Award.

Received in original form November 25, 2002

Received in final form April 14, 2003


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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