Serial CT in fibrosing alveolitis: prognostic significance of the initial pattern

In patients with fibrosing alveolitis, a reticular pattern on CT scans of the lungs correlates with histologic findings of fibrosis, whereas a ground-glass pattern has been reported to correlate with reversible inflammatory disease. The majority of patients with fibrosing alveolitis have a ground-glass component visible on CT scans, but response to therapy is infrequent. The aim of this study was to evaluate the prognostic significance of the relative extents of ground-glass and reticular patterns by analyzing serial changes in these CT appearances.

Serial CT scans were analyzed in 56 patients (21 with idiopathic pulmonary fibrosis and 35 with fibrosing alveolitis associated with systemic sclerosis). The relative extents of ground-glass and reticular patterns were assessed on the initial CT scan. Overall extent of abnormal lung and distribution of disease on initial CT scans were also categorized. Changes in extent and appearance of disease were evaluated in paired anatomically comparable CT sections and assessed independently by two observers; the median interval between scans was 16 months. Serial changes on CT were examined in relation to the initial pattern, extent, and distribution of disease seen on CT scans and in relation to trends in results of concurrent pulmonary function tests.

Changes in the extent of disease were due to regression of a ground-glass pattern in 18 patients, an increase in a reticular pattern in nine patients, and an increase in a ground-glass pattern in five patients. A reticular pattern did not regress in any patient. In treated patients, diminution in extent of disease, shown as regression of a ground-glass pattern, was seen most frequently when a ground-glass pattern was the most extensive abnormality at initial scanning (p < .002), independent of extent or distribution of disease seen on CT scans and the type of fibrosing alveolitis. When a ground-glass pattern was associated with an equally extensive reticular pattern, the extent of disease diminished with therapy in a minority of patients (5/13). Improvement in results of pulmonary function tests was associated with regression of a ground-glass pattern in the majority of patients (8/11).

These findings indicate that the prognostic significance of a ground-glass pattern depends on the extent of an associated reticular pattern and is independent of the extent and distribution of disease.