Decline in FEV1 in patients with PiZ alpha-1-antitrypsin deficiency: the Australian experience

Decline in FEV1 and hospitalized exacerbations in individuals with severe alpha-1 antitrypsin deficiency

Background and aim: The value of the forced expiratory volume in one second (FEV₁) is useful in the diagnosis and prognosis of chronic obstructive pulmonary disease (COPD). Previous studies on lung function in individuals with severe alpha-1 antitrypsin deficiency (AATD) have shown a variable annual decline in FEV₁ (∆FEV₁). The aim of this study was to analyze ∆FEV₁ and to identify risk factors for ∆FEV₁ in individuals with severe AATD.

Material and methods: Data on smoking habits, symptoms, results of lung function tests and exacerbations were obtained from the Swedish AATD Register and the Swedish National Patient Register (SNPR). The ∆FEV₁ was analyzed by random-effects modeling and adjusted for age and FEV₁ at baseline.

Results: One hundred and four (9%) current smokers, 539 (48%) ex-smokers and 489 (43%) never-smokers were included in the study and followed-up from 1991 to 2016. A total of 584 (52%) individuals with severe AATD had COPD at inclusion. The median (IQR) annual severe exacerbation rate was 0.66 (1.4). The adjusted mean ∆FEV₁ was significantly higher in the current smokers compared with the ex-smokers and never-smokers (70 [95% CI 56–83] vs 42 [95% CI 36–48] and 32 [95% CI 25–38) mL·yr⁻¹], in the middle–aged individuals compared with the young individuals (48 [95% CI 41–55] vs 32 [95% CI 18–45] mL·yr⁻¹), in the individuals with respiratory symptoms at inclusion compared with the asymptomatic individuals (46 [95% CI 40–52] vs 30 [95% CI 22–38]mL·yr⁻¹), and in the individuals with frequent exacerbations compared with those with infrequent exacerbations (57 [95% CI 47–68] vs 27 [95% CI 17–37] mL·yr⁻¹).

Conclusion: Active smoking, age, respiratory symptoms at baseline and repeated severe exacerbations of COPD are factors associated with an accelerated decline of lung function in individuals with severe AATD.

Secreted modular calcium-binding protein 2 haplotypes are associated with pulmonary function

RATIONALE

Previously reported linkage to FEV(1) (LOD score = 5.0) on 6q27 in the Framingham Heart Study (FHS) led us to explore a candidate gene, SMOC2, at 168.6 Mb.

OBJECTIVES

We tested association between SMOC2 polymorphisms and FEV(1) and FVC in unrelated FHS participants.

METHODS

Twenty single-nucleotide polymorphisms (SNPs) around SMOC2 were genotyped in 1,734 subjects.

MEASUREMENTS AND MAIN RESULTS

SNP data were analyzed using multiple linear regression models incorporating sex, age, body mass index, height, and smoking history as covariates, and analyses were repeated within strata of ever- and never-smokers. The minor allele of SNP rs1402 was associated with higher mean FEV(1) (p = 0.003) and FVC (p = 0.02) measures. In never-smoking subjects, association with higher measures was observed with the minor allele of rs747995 (FEV(1), p = 0.0006; FVC, p = 0.0008). These two SNPs lie in different haplotype blocks and reside in intron 4 of SMOC2. Haplotype analysis revealed a common G-T haplotype (rs747995-rs1402) with 77% frequency in never-smoking FHS subjects. The G-T haplotype was associated with reduction of 126 ml for FEV(1) (p = 0.0002) and 157 ml for FVC (p = 0.0002). The G-T haplotype was similarly associated in a set of never-smoking subjects from the Family Heart Study (FEV(1), p = 0.03; FVC, p = 0.03).

CONCLUSIONS

The replication of the association in two populations supports the possibility that SMOC2 might play an important role in the determination of FEV(1) and FVC.