Variation in Lung Function and Nutritional Decline in Cystic Fibrosis by Genotype: An Analysis of the Canadian Cystic Fibrosis Registry

Background: This study aimed to improve our understanding of the natural history of cystic fibrosis (CF) by comparing lung function and body mass index z-score (zBMI) between patients with different genotypes and identify a genotype with outcomes most comparable to homozygous ΔF508 patients.

Methods: Data was obtained from the Canadian CF Registry between January 1st 2007-January 1st 2016. Patients were categorized into one of five groups based on their genotype. A mixed-effects model was conducted with adjustments for age, sex, age of diagnosis, and baseline clinical measures.

Results: Among 2612 patients, those with non-mild forms of CF, and particularly adult patients with the same functional allele classification were found to have a lung function trajectory comparable to individuals with the homozygous ∆F508 genotype (annual change in percent predicted forced expiratory volume in 1 s of -0.83, 95% CI: -0.93, -0.73). The rates of zBMI change over the study period were not significantly different between the genotype groups.

Conclusion: This population-based study of Canadian CF patients provides adjusted rates of lung function decline and zBMI over ten years. The finding that there are different genotypes with comparable rates of lung function decline to patients of the homozygous ∆F508 group supports the use of multiple comparison groups to assess the long-term efficacy of emerging CF therapies.