The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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A decreased transfer coefficient of the lung for carbon monoxide (K(CO)) is associated with emphysema. We evaluated whether in heavy smokers, baseline K(CO) was associated with the progression of computed tomography (CT)-detected emphysema, and the progression of airflow limitation. Heavy smokers, mean ± sd 41.3 ± 18.7 pack-yrs, participating in a lung cancer screening trial underwent diffusion testing and CT scanning of the lungs. ⋯ Mean ± sd 15th percentile was -938 ± 19, absolute FEV₁/FVC was 71.6 ± 9% and K(CO) was 1.23 ± 0.25, which is 81.8 ± 16.5% of predicted. By interpolation, a one sd (0.25) lower K(CO) value at baseline predicted a 1.6 HU lower 15th percentile and a 0.78% lower FEV₁/FVC after follow-up (p < 0.001). A lower baseline K(CO) value is independently associated with a more rapid progression of emphysema and airflow limitation in heavy smokers.