Canada seeing the largest improvements in sickest patients with cystic fibrosis compared to U.S. and Europe

Canadians living with cystic fibrosis have better lung health than their American and European counterparts and their lung health has been improving over time according to a new study from The Hospital for Sick Children (SickKids). Dr. Lisa Strug, Associate Director of The Centre for Applied Genomics (TCAG) and Senior Scientist at SickKids was the principal investigator of the study published online February 5, 2018 in Thorax. She and lead author, University of Toronto graduate student Sangook Kim, took some time to tell us about their new research.

How do you measure lung health?

“Forced expiratory volume in one second”, also known as FEV1, is a typical measure of lung health. This tests how much air someone can exhale during a forced breath within the first second of exhaling. It’s usually represented as a ratio of the FEV1 of a patient with cystic fibrosis to a predicted FEV1 of a healthy individual sharing the same age, sex, race and height. It allows clinicians to see how the lung health of their patients compare to the healthy population but doesn’t show how patients with cystic fibrosis compare to one another.

What was your goal with this new research?

Our primary goal was to use a different approach to interpret the lung health of an individual with cystic fibrosis from FEV1 measurements, which wouldn’t rely on a healthy population. Rather, we wanted to develop a way for patients with cystic fibrosis to compare their measurements to one another. To that end, we’ve created an online tool for patients and clinicians to make this information accessible so lung health in any patient can be determined against other patients with cystic fibrosis in Canada.

Using this new approach, we also wanted to determine how the lung health of Canadians with cystic fibrosis has changed over time and whether their lung health is better than individuals with cystic fibrosis in the U.S. and Europe.

What did you find?

We looked at the lung health of Canadians with cystic fibrosis over two time periods, 2000-2007 and 2008-2014, when we know average survival had been steadily improving. Over this time, we observed that lung health of Canadians was also steadily improving, and that these improvements in lung health were larger for those with the lowest lung function and particularly for males.

When compared with the cystic fibrosis populations of the U.S. and Europe over the same time period, we found Canadians with cystic fibrosis generally had better lung health. In particular, the Canadian patients with the lowest lung function showed the biggest gap between patients in the U.S. and Europe, indicating Canada is having the largest improvements among the patients who are sickest.

What are your next steps?

Differences in lung health between males and females is a well-known phenomenon, but we were surprised to discover there was a difference in lung health improvements between males and females. Improvements over time were more moderate for female patients with cystic fibrosis compared to males and lung health improvements were not significant for females with the best lung function. Future research will need to explore why these sex differences exist, and to extend and use this measure of lung health to better understand differences in lung disease severity between patients.

The new tool we developed to compare lung health of cystic fibrosis patients to other patients in Canada will complement current measures of lung health, to better support clinical care and decision-making.

This research was supported by the Canadian Institutes of Health Research (CIHR), the Natural Sciences and Engineering Research Council of Canada (NSERC), Cystic Fibrosis Canada and SickKids Foundation. This paper is an example of how SickKids is contributing to making Ontario Healthier, Wealthier and Smarter. www.healthierwealthiersmarter.ca