Predictors of mortality in α₁-antitrypsin deficiency

Abstract

Background: Lung density measurements by computed tomography have previously been found to be a more sensitive indicator of disease progression in emphysema of α₁-antitrypsin deficiency than lung function measurements. The aim of this study was to investigate the predictive potential of several parameters, including CT scanning, for mortality in patients with severe α₁-antitrypsin deficiency.

Methods: Over a 5 year period, 256 patients with α₁-antitrypsin deficiency (PiZ phenotype) were assessed, of whom 254 underwent lung function testing and 197 had thoracic CT scans. Lung function, CT scans, health status (St George’s Respiratory Questionnaire, SGRQ), and other clinical data of survivors and non-survivors were compared and these parameters were applied to survival analyses.

Results: There were 22 deaths in this patient cohort, 10 of which were classified as “respiratory” deaths. Baseline lung function parameters (forced expiratory volume in 1 second (FEV₁), carbon monoxide transfer coefficient (Kco)), and CT scores were significantly lower in the non-survivors than in the survivors. 170 of the 256 patients had complete data for entry into multiple regression analyses (Cox proportional hazards model). In the univariate analysis, upper zone expiratory scan had the best association with all cause (p = 0.001) and respiratory mortality (p<0.001), whereas FEV₁ (p = 0.158 all cause, 0.015 respiratory) and Kco (p = 0.002 all cause, 0.012 respiratory) had poorer associations with mortality. Only age gave further independent predictive information regarding all cause or respiratory mortality when the CT scan was entered into the survival analyses.

Conclusions: CT scanning predicts respiratory and all cause mortality in α₁-antitrypsin deficiency and appears to be superior to lung function parameters, especially FEV₁.