Canadians with cystic fibrosis have a significant survival advantage over American patients

1. After adjusting for risk factors associated with survival, Canadian patients had a median age of survival that was 10 years greater than in the United States.

2. The authors hypothesized that differential access to transplantation, increased post-transplant survival, and differences in health care systems may partially explain the Canadian survival advantage.

Evidence Rating Level: 2 (Good)

Study Rundown: Life expectancy for patients diagnosed with cystic fibrosis (CF) is continuing to increase. In 2011, the median age of survival for patients with CF in the US Cystic Fibrosis Foundation Patient Registry (CFFPR) was 36.8 years, compared to 48.5 years in the Canadian Cystic Fibrosis Registry (CCFR). The differences between countries emphasizes that life expectancy depends not only on a patient’s characteristics, but also on his or her access to medical care and medications, which vary both within and among countries. However, directly comparing estimates of median age of survival between national registry reports poses problems; risk factors associated with survival, as well as inherent differences in methodologies, must be taken into account. To address this problem, the authors of the study aimed to determine whether using a standardized approach to data processing and survival calculations would confirm the observed difference between Canada the United States. They also aimed to identify any contributing factors to this survival gap if a true difference existed. The main limitation of this study is its ascertainment bias; if any of the registries are missing key data or nonrandom loss to follow up, the results of the study may be affected. Overall, the results of the study suggest that a true difference in CF survival exists between Canada and the US, even after adjusting for known risk factors. Additional studies are required to confirm contributors to this gap in patient outcome.

Click to read the study in the Annals of Internal Medicine

Relevant Reading: A contemporary survival analysis of individuals with cystic fibrosis: a cohort study

In-Depth [retrospective cohort]: In this population-based study, data was collected from 42 Canadian CF clinics and 110 U.S. CF care centers, using the CCFR (n = 5941) and CFFPR (n = 45 448) from 1990 to 2013. Survival rates between Canadian and American patients were compared using cox proportional hazards models. Risk factors associated with survival were taken into account and adjusted for using multivariate models. In general, Canadians with CF were shown to have a significant survival advantage over American patients. From 2009 to 2013, the median age of survival in Canada was 50.9 compared to 40.6 years in the U.S. The adjusted risk for death was also 34% lower in Canada compared to the U.S. (HR 0.66; 95%CI 0.54 to 0.81). While adjusting for all other risk factors did not change the differences observed in patient outcome between countries, differences in survival did vary depending on U.S. patients’ private insurance status.

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