title: The impact of switching to the new global lung function initiative equations on spirometry results in the UK CF registry.
abstract: BACKGROUND
  The Quanjer et al. Global Lung Function Initiative (GLI)-2012 multi-ethnic all-age reference equations for spirometry are endorsed by all major respiratory societies and are the new gold standard. Before the GLI equations are implemented for use in CF patients, the impact of changing equations from those currently used needs to be better understood.
  
  
  METHODS
  Annual review data submitted to the UK CF Trust Registry between 2007 and 2011 were used to calculate %predicted FEV1, FVC and FEV1/FVC using three widely used reference equations (Wang-Hankinson and Knudson) and the new GLI-2012 equations.
  
  
  RESULTS
  Overall, Knudson and Wang equations overestimated %predicted values in paediatric patients, such that a greater proportion of patients had lung function values in the normal range. Within individual patients, the impact of switching equations varied greatly depending on the patients' age, and which equations were used.
  
  
  CONCLUSIONS
  A unified approach to interpreting spirometric lung function measurements would help facilitate more appropriate comparison both within and between centres and countries. Interpretation of longitudinal measurements using a continuous reference equation across all-ages, like the GLI, may further improve our understanding of CF lung disease.
authors: Hospital for Sick Children, Toronto, Canada. Electronic address: Sanja.Stanojevic@sickkids.ca.
authors: Sanja
authors: S
authors: Stanojevic
authors: UCL Institute of Child Health, London, UK.
authors: Janet
authors: J
authors: Stocks
authors: UCL Institute of Child Health, London, UK.
authors: Vassiliki
authors: V
authors: Bountziouka
authors: UCL Institute of Child Health, London, UK; Great Ormond Street Hospital for Children NHS Trust, London, UK.
authors: Paul
authors: P
authors: Aurora
authors: UCL Institute of Child Health, London, UK; Great Ormond Street Hospital for Children NHS Trust, London, UK.
authors: Jane
authors: J
authors: Kirkby
authors: Royal Victoria Infirmary, Newcastle upon Tyne, UK.
authors: Stephen
authors: S
authors: Bourke
authors: Royal Brompton Hospital, London, UK.
authors: Siobhán B
authors: SB
authors: Carr
authors: Cystic Fibrosis Trust (UK), London, UK.
authors: Elaine
authors: E
authors: Gunn
authors: Great Ormond Street Hospital for Children NHS Trust, London, UK.
authors: Ammani
authors: A
authors: Prasad
authors: Seattle Children's Hospital, Seattle, WA, USA.
authors: Margaret
authors: M
authors: Rosenfeld
authors: Cystic Fibrosis Trust (UK), London, UK.
authors: Diana
authors: D
authors: Bilton
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003550:Cystic Fibrosis / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume; D006779:Hospitals, Public; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012016:Reference Values; D012042:Registries / Q000592:standards* / Q000706:statistics & numerical data*; D013147:Spirometry / Q000592:standards*; D006113:United Kingdom; D055815:Young Adult
keywords: Cystic fibrosis; Reference values; Spirometry