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Progress of emphysema in severe alpha 1-antitrypsin deficiency as assessed by annual CT
A Dirksen1, M Friis, K P Olesen
1Department of Respiratory Medicine, Bispebjerg Hospital, Copenhagen, Denmark.
Purpose:
To assess serial CT as a measure of the progress of emphysema in patients with severe alpha 1-antitrypsin deficiency (phenotype PiZ).
Material And Methods:
In a randomized placebo-controlled study of alpha 1-antitrypsin augmentation therapy, 22 patients with moderate emphysema were followed for 2-4 years with an annual lung CT. The images were analysed by means of semiautomatic lung detection, and the degree of emphysema was quantitated by the density-mask and the percentile methods. The influence of lung volume was standardised by a regression model.
Results:
A highly significant decline in Hounsfield units (HU) was found in low-density areas, corresponding to a mean (SE) annual loss of lung tissue of 2.1 (0.4) g/l lung volume. Analysis of a single slice at 5 cm below the level of the carina gave comparable results: 2.4 (0.4) g/l.
Conclusion:
Serial CT is a sensitive measure of the progress of emphysema in patients with severe alpha 1-antitrypsin deficiency.