Pulmonary Abnormalities on High-Resolution CT Demonstrate More Rapid Decline Than FEV1 in Adults With Cystic Fibrosis: Discussion

Severity of bronchiectasis, extent of mucus plugging, sacculations/abscesses, generations of bronchial divisions involved, and air trapping demonstrated systematic differences between readers on Bland and Altman plots. Observer 1 scored extent of mucus plugging and air trapping worse on average than observer 2, and this was more pronounced for mild scores. Observer 2 scored severity of bronchiectasis, sacculations/abscesses, and generations of bronchial divisions involved worse on average than observer 1. For severity of bronchiectasis and generations of bronchial divisions involved, this was more pronounced for moderate scores; for sacculations/abscesses, this was more pronounced for severe scores. Reading here
The major findings of this study are as follows: (1) 15% of adults in our cohort demonstrated stable spirometry results but deteriorating HRCT scores; (2) in the remaining adults with declining FEV1, HRCT scores for several abnormalities deteriorated at a more rapid rate; and (3) the rate of decline of individual HRCT abnormalities differed depending on the severity of lung function impairment. In recent innovative work, de Jong et al evaluated a Swedish group of children and adults with CF over time, and found several CT abnormalities as well as total HRCT score declined in the adult cohort while FEV1 remained stable. Six patients in our study demonstrated stable FEV1 but deterioration in many HRCT abnormalities, similar to findings in the Swedish cohort. In contrast, most patients in our adult CF population had moderate-to-severe lung impairment with chronic loss of lung function over time. Nevertheless, even in this group several CT abnormalities as well as total HRCT scores declined more rapidly than FEV1.
We subgrouped patients into mild and moderate-to-severe lung function impairment and found certain HRCT abnormalities worsened in patients with mild impairment, while others worsened in patients with moderate-to-severe impairment. In particular, based on the degree of lung impairment, the extent of bronchiectasis deteriorated more markedly in the mildly impaired group, whereas the severity of bronchiectasis deteriorated more markedly in the mod-erate-to-severely impaired group. de Jong et al found that peripheral bronchiectasis showed the most significant deterioration on HRCT over time in their adult Swedish cohort. Although our scoring system did not assess abnormalities in terms of central and peripheral locations, both extent and severity of bronchiectasis deteriorated significantly compared with FEV1. Whichever scoring system is utilized, both studies would appear to suggest that bronchiectasis is one of the most important factors in the longitudinal deterioration in CF lung disease.

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