Gaps in Cystic Fibrosis Care Are Associated with Reduced Lung Function in the U.S. Cystic Fibrosis Foundation Patient Registry

Abstract

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.

Keywords: care fragmentation; cystic fibrosis; lung function decline.

Figure 1.

Description of the study cohort, derived from people with cystic fibrosis in the CFFPR between 2004 and 2016. The figure includes a description of patient-level and encounter-level exclusions. BMI = body mass index; CF = cystic fibrosis; CFFPR = Cystic Fibrosis Foundation Patient Registry; FEV₁PP = percentage predicted forced expiratory volume in 1 second; PFT = pulmonary lung function using FEV₁PP.

Figure 2.

Distribution of discontinuous care (⩾12-month gap) among people with cystic fibrosis by age group between 2004 and 2016. Reported proportions are restricted to each age stratum and do not reflect cumulative lifetime care continuity. Adapted from Reference (27).

Figure 3.

Estimated percentage predicted forced expiratory volume in 1 second (FEV₁PP) values associated with continuous (solid line) and discontinuous (dashed line) care by age among 24,328 individuals with cystic fibrosis in the Cystic Fibrosis Foundation Patient Registry between 2004 and 2016. Shaded area indicates 95% confidence bounds. Estimated FEV₁PP values are given for a typical person (i.e., at average values for covariates). (A) Estimated FEV₁PP curves for ages 6 to 45 (Model 2). (B) Enlarged estimated FEV₁PP curve showing ages 15–25 years (Model 2). (C) Estimated FEV₁PP curves showing ages 15–25 years for F508del homozygotes (Model 3). (D) Estimated FEV₁PP curves showing age 15–25 for F508del heterozygotes (Model 3). Adapted from Reference (27).