Augmentation Therapy for α₁ Antitrypsin Deficiency: A Meta-Analysis

Abstract

Background. Augmentation with exogenous α₁-antitrypsin (α₁-AT) is the only specific therapy for α₁-AT deficiency. Uncertainty persists concerning its effectiveness. Purpose. To test the hypothesis that augmentation therapy in patients with α₁-AT deficiency slows the decline in FEV₁. Study Selection. Randomized and nonrandomized clinical studies with either parallel-group design or single cohort pre-post design were eligible if they compared augmentation therapy with a control regimen and if long-term (> 1 y) longitudinal FEV₁ follow-up data were collected. Data Synthesis. FEV₁ data from five trials with 1509 patients were combined by random effects meta-analysis. The decline in FEV₁ was slower by 23% (absolute difference, 13.4 ml/year; CI, 1.5 to 25.3 ml/year) among all patients receiving augmentation therapy. This overall protective effect reflected predominantly the results in the subset of patients with baseline FEV₁ 30–65% of predicted. In that subset, augmentation was associated with a 26% reduction in rate of FEV₁ decline (absolute difference, 17.9 ml/year; CI, 9.6 to 26.1 ml/year). Similar trends amongst patients with baseline FEV₁ percent of predicted < 30% or > 65% were not statistically significant. Conclusions. This meta-analysis supports the conclusion that augmentation can slow lung function decline in patients with AAT deficiency Patients with moderate obstruction are most likely to benefit.