Rationale: In cystic fibrosis (CF), lung disease is the predominant cause of morbidity and mortality. Little is known about the spectrum of structural abnormalities on CT scans from patients with CF with severe advanced lung disease (SALD). No specific CT scoring system for SALD is available. Objectives: To design a quantitative CT scoring system for SALD, to determine the spectrum of structural abnormalities in patients with SALD and to correlate the SALD system with an existing scoring system for mild CF lung disease and pulmonary function tests (PFTs). Methods: 57 patients with CF contributed one CT made during screening for lung transplantation. For the SALD system, lung tissue was divided into four components: infection/inflammation (including bronchiectasis, airway wall thickening, mucus and consolidations), air trapping/ hypoperfusion, bulla/cysts and normal/hyperperfused tissue. The volume proportion of the components was estimated on a 0-100% scale; mean volumes for the whole lung were computed. Scores were correlated with Brody-II scores and PFTs. Results: The SALD system identified a wide spectrum of structural abnormalities ranging from predominantly infection/inflammation to predominantly air trapping/ hypoperfusion. SALD infection/inflammation scores correlated with Brody-II scores (r s = 0.36-0.64) and SALD normal/hyperperfusion scores correlated with forced expiratory volume in 1 s (FEV 1 ; r s = 0.37). Reproducibility for both systems was good. Conclusions: A CT scoring system was developed to characterise the structural abnormalities in patients with SALD. A wide spectrum was observed in SALD, ranging from predominantly air trapping to predominantly infection/inflammation-related changes. This spectrum may have clinical implications for patients with SALD.

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In this pilot study, CT scores from end-expiratory and end-inspiratory CT match closely, suggesting that ultra-low-dose end-expiratory CT alone may be sufficient for monitoring CF-related lung disease. This would help reduce radiation dose for a single investigation by up to 75%.

CT score INF correlates with survival, and adds to the predictive value of LAS.