Spirometric and gas transfer discordance in α1-antitrypsin deficiency: patient characteristics and progression

BACKGROUND: Phenotypic differences in physiologic, radiologic, and clinical characteristics are increasingly recognized in COPD. The factors associated with a 1 -antitrypsin deficiency (A1AD)physiologic phenotypes and how they progress with time have yet to be explained.

METHODS: The study comprised 530 patients with the homozygote Z variant (PiZZ) A1AD; 255 patients had greater than or equal to 3 years of data for longitudinal analysis. Patients were categorized into four groups using lower limits of normal for the carbon monoxide transfer coefficient (K ) and postbronchodilator FEV 1 /FVC ratio. Group comparisons were undertaken for demographic, clinical, physiologic, health status, survival, and CT scan data.

RESULTS: Groups with normal lung function or isolated gas transfer defect had the lowest smoking history , least emphysema, and best health status. The group with air flow obstruction (AO) alone had a greater smoking history, more emphysema, and worse health status compared with the normal group. The group with combined AO and gas transfer defect was the worst. The group with AO alone had a faster subsequent decline in K CO than the normal group ( P =.002) and the group with both AO and reduced gas transfer ( P < .001) and was more likely to change groups with time(62% moved to group B). Lower baseline K CO and male sex predicted 89% of the movement to the group with both physiologic abnormalities.

CONCLUSIONS: There are distinct physiologic phenotypes in A1AD with differing demographic features that relate to progression.