Small airway function in patients with alpha1-antitrypsin deficiency. Correlation with quality of life and exercise capacity.

<bold>Introduction:</bold> Alpha1-antitrypsin deficiency (AATD) is associated with panlobular emphysema, predisposing to COPD. Small airway disease (SAD), a hallmark of COPD, precedes emphysema formation. Oscillometry, a lung function technique sensitive to SAD, correlates with quality of life (QoL) better than spirometry. The value of oscillometry in AATD is unknown. We assessed the relationship of oscillometry with QoL and exercise capacity in AATD. <bold>Methods:</bold> 19 AATD (PiZZ genotype) patients and 10 non-AATD COPD patients (matched for age, FEV1%) undertook the St’ George Respiratory QoL Questionnaire, oscillometry and multiple breath nitrogen washout, while historical body plethysmography data (spirometry, lung volumes, gas transfer) were registered within one year from study visit. A 1-minute sit-to-stand test (STS) was performed. Chest CT scans were retrieved from medical file and densitometry analysis undertaken. <bold>Results:</bold> In AATD, radiographic emphysema was mostly correlated with TLco% (r=-0.67, p=0.003). QoL was more strongly correlated with TLco% (r=-0.58, p=0.008), followed by FEV1% (r=-0.52, p=0.023). Combining R5-R20 with TLco% abnormality identified a group of patients with the worst QoL. STS repetitions correlated with X5 (r=0.61, p=0.009). Compared to non-AATD COPD, patients with AATD had worse TLco% (p=0.035). In AATD, lower lobe emphysema was associated with worse FEV1% (p=0.02) and more hyperinflation (RV/TLC, p=0.005), compared to upper lobe. <bold>Conclusion:</bold> Combining the oscillometric parameter of SAD (R5-R20) with TLco% abnormality identifies a group of AATD patients with the most affected QoL.