Gaps in Cystic Fibrosis Care Are Associated with Reduced Lung Function in the US Cystic Fibrosis Foundation Patient Registry

Rationale: Cystic fibrosis (CF) is a genetic disease leading to progressive lung function loss and early mortality. Many clinical and demographic variables are associated with lung function decline, but little is known about the effects of prolonged periods of missed care. Objectives: To determine if missed care in the Cystic Fibrosis Foundation Patient Registry (CFFPR) is associated with decreased lung function at follow-up visits. Methods: Deidentified CFFPR data for 2004-2016 were analyzed, with the exposure of interest being >= 12-month gap in CFFPR data. We modeled percentage predicted forced expiratory volume in 1 second using longitudinal semiparametric modeling with natural cubic splines for age (knots at quantiles) and with subject-specific random effects, adjusted for sex and CFTR (cystic fibrosis transmembrane conductance regulator) genotype, race, and ethnicity and included time-varying covariates for gaps in care, insurance type, underweight body mass index, CF-related diabetes status, and chronic infections. Results: A total of 24,328 individuals with 1,082,899 encounters in the CFFPR met inclusion criteria. In the cohort, 8,413 (35%) individuals had at least a single >= 12-month episode of discontinuity, whereas 15,915 (65%) had continuous care. Of the encounters preceded by a 12-month gap, 75.8% occurred in patients 18 years and older. Compared with those with continuous care, those with a discontinuous care episode had a lower follow-up percentage predicted forced expiratory volume in 1 second at the index visit (-0.81%; 95% confidence interval, -1.00,-0.61) after adjustment for other variables. The magnitude of this difference was much greater (-2.1%; 95% confidence interval, -1.5,-2.7) in young adult F508del homozygotes. Conclusions: There was a high rate of >= 12-month gap in care, especially in adults, documented in the CFFPR. Discontinuous care identified in the CFFPR was strongly associated with decreased lung function, especially in adolescents and young adults homozygous for the F508del CFTR mutation. This may have implications for identifying and treating people with lengthy gaps in care and may have implications for CFF care recommendations.