Incidence of emphysema at necropsy as assessed by point-counting.

The lungs from an unselected group of necropsies were fixed in inflation by boiling formaldehyde vapour, and the percentage of emphysema was determined by macroscopic point-counting. The emphysema was categorized into alveolar, centrilobular, bullous, and mixed'. The term mixed' emphysema was applied to cases which had a combination of two or all of the three forms. Quantitative criteria were used in the diagnosis of emphysema. `Significant' emphysema was defined as destruction of the lung parenchyma by 5% or more of centrilobular or 10% or more of alveolar or bullous emphysema. Using these criteria, the overall incidence of emphysema in both sexes was 24%, the incidence in men being 35% and in women 9%. Alveolar emphysema was present in 25% of males and in 3% of females. The corresponding figures for centrilobular emphysema were 6% and 3%. Comparison of the present investigation with other studies suggests that there are geographical differences in the incidence of the alveolar and centrilobular forms of the disease.