Background
In 2011, the median age of survival in cystic fibrosis (CF) reported in the United States (US) was 36.8 years compared to 48.5 years in Canada; however direct comparison of survival estimates between national registries is challenging because of inherent differences in methodologies used, data processing techniques, and ascertainment bias.
Objectives
To use a standardized approach to calculate CF survival estimates and to explore differences between Canada and the United States (US).
Design
Population-based study.
Setting
42 Canadian CF clinics and 110 CF care centers in the US.
Patients
Patients followed in the Canadian CF Registry (CCFR) and the US Cystic Fibrosis Foundation (CFF) Patient Registry (CFFPR) between 1990 and 2013.
Measurement
Cox proportional hazards models were used to compare survival between patients followed in the CCFR (n=5,941) and CFFPR (n=45,448). Multivariable models were used to adjust for factors known to be associated with survival.
Results
Median age of survival in patients with CF increased in both countries between 1990 and 2013; however in 1995 and 2005, survival in Canada increased at a faster rate relative to the US (p<0.001). Using contemporary data from 2009-2013, the median age of survival in Canada was ten years greater than the US (50.9 vs. 40.6 years, respectively). The adjusted risk of death was 34% lower in Canada compared to the US (hazard ratio 0.66, 95% CI 0.54-0.81). A greater proportion of patients had transplants in Canada (10.3% vs. 6.5% respectively, SD 13.7). Differences in survival between US and Canadian patients varied according to the US patients' insurance status.
Limitations
Ascertainment bias as a result of missing data or non-random lost to follow-up could impact the results.
Conclusions
Differences in CF survival between Canada and the US persisted after adjusting for risk factors associated with survival. Differential access to transplantation, improved post-transplant survival and differences in the healthcare systems may, in part, explain the Canadian survival advantage.
BACKGROUND AND OBJECTIVES: Cystic fibrosis transmembrane conductance regulator-related metabolic syndrome (CRMS) describes asymptomatic infants with a positive cystic fibrosis (CF) newborn screen (NBS) but inconclusive diagnostic testing for CF. Little is known about the epidemiology and outcomes of CRMS. The goal of this study was to determine the prevalence, clinical features, and short-term outcomes of infants with CRMS.
METHODS:We analyzed data from the US CF Foundation Patient Registry (CFFPR) from 2010 to 2012. We compared demographic, diagnostic, anthropometric, health care utilization, microbiology, and treatment characteristics between infants with CF and infants with CRMS.
Background
People with cystic fibrosis are managed differently in the US and UK providing an opportunity to learn from differences in practice patterns.
Objectives
To compare cross-sectional demographics, practice patterns and clinical outcomes between US and UK cystic fibrosis patients.
Methods
This was a cross-sectional study using 2010 data from patients in the US Cystic Fibrosis Foundation and the UK Cystic Fibrosis patient registries. The a priori outcome measures of interest were lung function and nutritional status. Descriptive statistics and two sample comparisons were performed. Stratification and multivariable linear regression was used to adjust for confounding.
Results
The study cohort included 13,777 children and 11,058 adults from the US and 3,968 children and 3,965 adults from the UK. In children, mean body mass index percentiles were similar. Lung function (FEV1 and FVC% predicted) was significantly higher in US patients ages 6 through 25 years of age. In a regression model adjusted for only age, FEV1% predicted was on average 3.31% of predicted (95% CI: 2.65, 3.96) higher in the US compared to the UK. When adjusted for age, age at diagnosis, gender, pancreatic insufficiency and genotype, FEV1% predicted was on average 3.03% of predicted (95% CI: 2.37, 3.69) higher in the US compared to the UK These differences persisted despite adjustment for possible confounders. Hypertonic saline and dornase alfa were much more commonly prescribed in US children.
Conclusions
Children and young adults with cystic fibrosis have better lung function in the US compared to the UK despite similar nutritional status.
The reasons for the observed improvements, and catch-up in the United States, are likely multifactorial and include the introduction of high-fat, high-calorie diets; introduction of newborn screening; and/or improved access to care for CF children in the United States.
Objective
Our objective was to quantify the effect of different statistical techniques, inclusion/exclusion criteria and missing data on the predicted median survival age.
Study Design and Setting
Using the Canadian CF registry (CCFR), the median age of survival was calculated using both the Cox Proportional Hazards (PH) and the life-table methods. Through simulations, we examined how the median age of survival would change when: 1) patients were excluded, 2) death dates were inaccurate, 3) patients were lost to follow-up, 4) entire years with no clinic visits were excluded even if the patient had a visit in subsequent years, and 5) censoring patients at their date of transplant. Simulations were run assuming 5% to 35% of data were affected by each scenario.
Results
Over the period 2009 to 2013, there were 4,666 individuals in the CCFR with 240 deaths. The observed median age of survival calculated by the Cox PH method was 50.9 (95% CI: 47.4–54.3) and 50.5 from the life-table method (95% CI: 47.5–53.5). Censoring patients at their transplant date overestimated the median age of survival by 7.2 years (58.1, 95% CI: 53.3–64.7). Simulations determined that by missing just 15% of deaths, the median age of survival can be overestimated by 3.5 years (54.4, 95% CI: 54.2, 56.1), and having 25% of patients lost to follow-up can underestimate the median age of survival by 3.3 years (47.6, 95% CI: 46.8–47.7).
Conclusions
We present several recommendations to assist national CF registries in calculating and reporting the median age of survival in a standardized fashion. It is imperative to state the statistical method used as well as the proportion lost to follow-up and the treatment of missing data and transplanted patients. Registries must be diligent in their data collection as incomplete data can lead to over and underestimation of survival.
In the United States, the majority of individuals transferring from pediatric to adult CF care do so between ages 18 and 21 years. A minority had a gap greater than or equal to 365 days during transfer to adult care, suggesting that most did not have a disruption in recommended quarterly care visits during the transfer period. Risk factors for prolonged gaps in care include younger age at transfer, lack of health insurance, and relocation. Care coordination during transition in CF may minimize lapses in care by identifying and more closely addressing the needs of individuals at highest risk.
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