title: Improvements in lung function and height among cohorts of 6-year-olds with cystic fibrosis from 1994 to 2012.
abstract: OBJECTIVE
  To characterize spirometry and height changes in cohorts of 6-year-old children with cystic fibrosis (CF).
  
  
  METHODS
  Global Lung Initiative forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC, and the Centers for Disease Control and Prevention height-for-age (HFA) z-scores were generated for 6-year-old children from the Cystic Fibrosis Foundation Patient Registry each year between 1994 and 2012. Z-score mean differences were analyzed by the t test, and time trends of means were analyzed by least squares regression for all children and for subgroups of sex, F508del mutation genotype, Medicaid insurance, and prenatal/newborn screening identification. Z-score distributions were compared using the 2-sample Kolmogorov-Smirnov test.
  
  
  RESULTS
  A total of 11 670 children with CF were studied, of whom 50.5% were males, 50.2% had the F508del/F508del genotype, and 46.6% were insured by Medicaid. Mean HFA, FEV1, and FVC z-scores increased significantly over the period in the entire cohort and in all subgroups (P < .001), but FEV1/FVC z-scores were below normal and did not change significantly. In 2012, children identified by screening had significantly higher mean HFA (P = .002), FEV1 (P < .001), and FVC (P < .001) z-scores compared with children not screened, with 90% of FVC and 71.4% of FEV1z-scores greater than predicted by the normal distribution. FEV1/FVC z-scores were not different between the children who were and were not screened.
  
  
  CONCLUSIONS
  Consistent, significant increases in HFA, FEV1, and FVC occurred between 1994 and 2012, but FEV1/FVC, a measure of airway obstruction, did not change appreciably during this period. FVC and FEV1z-score distributions suggest that normative equation reference populations underpredict lung volumes of children with CF, but the reasons for this remain unclear.
authors.affiliation: Pediatrics, Case Western Reserve University School of Medicine, Cleveland, OH. Electronic address: drv15@case.edu.
authors.forename: Donald R
authors.initials: DR
authors.lastname: VanDevanter
authors.affiliation: Medical Affairs and Statistical Analysis, ICON Clinical Research, San Francisco, CA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Pasta
authors.affiliation: Pediatrics, Case Western Reserve University School of Medicine, Cleveland, OH; Pediatrics, Rainbow Babies and Children's Hospital, Cleveland, OH.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Konstan
mesh_terms: D001827:Body Height; D002648:Child; D003550:Cystic Fibrosis / Q000503:physiopathology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008297:Male; D015997:Neonatal Screening; D013147:Spirometry; D014797:Vital Capacity