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Reference percentiles of FEV1 for the Canadian cystic fibrosis population: comparisons across time and countries
  1. Sang-Ook Kim1,2,
  2. Mary Corey2,
  3. Anne L Stephenson3,4,
  4. Lisa J Strug1,2
  1. 1 Division of Biostatistics, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
  2. 2 Research Institute, The Hospital for Sick Children, Toronto, Canada
  3. 3 Department of Respirology, Adult Cystic Fibrosis Program, St. Michael’s Hospital, Toronto, Canada
  4. 4 Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada
  1. Correspondence to Dr Anne L Stephenson, St. Michael’s Hospital, Toronto, ON M5B 1W8, Canada; stephensona{at} and Dr Lisa J Strug, Research Institute, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada; lisa.strug{at}


Background Forced expiratory volume in 1 s (FEV1) indicates lung health in cystic fibrosis (CF). FEV1 is commonly communicated as a per cent predicted of a healthy individual sharing the same age, sex, race and height. CF-specific reference equations are complementary and calibrate a patient’s FEV1 to that of their CF peers.

Objectives (1) To derive Canadian CF-specific FEV1 reference percentiles (FEV1%iles), (2) characterize how they have changed over time and (3) compare the Canadian FEV1%iles to those for USA and European CF populations.

Method CF FEV1%iles are calculated using the Canadian CF Registry and quantile regression.

Results The Canadian FEV1%iles demonstrated better lung function in more recent time periods within Canada, especially below the 50% percentile and in males. When compared to USA and European FEV1%iles for the same time period, Canadian FEV1%iles were higher.

Conclusion CF-specific FEV1%iles can provide useful information about changes in lung health. An online calculator (available at makes these FEV1%iles accessible.

  • cystic fibrosis
  • respiratory measurement

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  • Contributors All authors contributed to the data analysis, manuscript preparation and revisions. All authors have approved the final version of this paper.

  • Funding This work was funded by grants to LJS from the Canadian Institutes of Health Research (CIHR; MOP-258916), the Natural Sciences and Engineering Research Council of Canada (NSERC; 371399-2009) and Cystic Fibrosis Canada (#2626).

  • Competing interests None declared.

  • Ethics approval Research Ethics Board of Hospital for Sick Children, Toronto, Canada.

  • Provenance and peer review Not commissioned; externally peer reviewed.