title: An update of the statistical methods underlying the FELS method of skeletal maturity assessment.
abstract: BACKGROUND
  Evaluation of skeletal maturity provides clinicians and researchers a window into the developmental progress of the skeleton. The FELS method for maturity assessment provides a point estimate and standard error based on 98 skeletal indicators.
  
  
  OBJECTIVE
  This paper outlines the statistical methodology used by the original FELS method and evaluates improvements that address the following: serial correlation in the calibration sample is now considered, a Bayesian estimation method is now employed to improve estimation near ages 0 and 18 years and uncertainty in the calibration due to sampling is now accounted for when computing confidence limits.
  
  
  METHODS
  The original FELS method was calibrated using 677 Fels Longitudinal Study participants. In the improved method, serial correlation is accounted for using GEE, a Bayesian analysis with a prior centred on chronological age is used and the bootstrap is used to account for all sources of variation.
  
  
  RESULTS
  Accounting for serial correlation resulted in larger slopes for ordinal indicators. The Bayesian paradigm led to narrower confidence limits and a natural interpretation of skeletal age. Sampling variability in the calibration parameters was negligible.
  
  
  CONCLUSIONS
  Improvements to the statistical basis of the FELS method provide a more effective method of estimating skeletal maturity.
authors.affiliation: Division of Morphological Sciences and Biostatistics, Lifespan Health Research Center, Department of Community Health and.
authors.forename: Ramzi W
authors.initials: RW
authors.lastname: Nahhas
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Sherwood
authors.forename: Wm Cameron
authors.initials: WC
authors.lastname: Chumlea
authors.forename: Dana L
authors.initials: DL
authors.lastname: Duren
mesh_terms: D000293:Adolescent; D000365:Age Determination by Skeleton / Q000379:methods*; D001499:Bayes Theorem; D001846:Bone Development; D002138:Calibration; D002648:Child; D002675:Child, Preschool; D006801:Humans; D008137:Longitudinal Studies; D008954:Models, Biological; D015233:Models, Statistical