title: Nationwide age references for sitting height, leg length, and sitting height/height ratio, and their diagnostic value for disproportionate growth disorders.
abstract: OBJECTIVE
  To obtain age references for sitting height (SH), leg length (LL), and SH/H ratio in the Netherlands; to evaluate how SH standard deviation score (SDS), LL SDS, SH/H SDS, and SH/LL SDS are related to height SDS; and to study the usefulness of height corrected SH/H cut-off lines to detect Marfan syndrome and hypochondroplasia.
  
  
  METHODS
  Cross-sectional data on height and sitting height were collected from 14,500 children of Dutch origin in the age range 0-21 years. Reference SD charts were constructed by the LMS method. Correlations were analysed in three age groups. SH/H data from patients with Marfan syndrome and genetically confirmed hypochondroplasia were compared with height corrected SH/H references.
  
  
  RESULTS
  A positive association was observed between H SDS, SH SDS, and LL SDS in all age groups. There was a negative correlation between SH/H SDS and height SDS. In short children with a height SDS <-2 SDS, a cut-off limit of +2.5 SD leads to a more acceptable percentage of false positive results. In exceptionally tall children, a cut-off limit of -2.2 SDS can be used. Alternatively, a nomogram of SH/H SDS versus H SDS can be helpful. The sensitivity of the height corrected cut-off lines for hypochondroplasia was 80% and for Marfan syndrome only 30%.
  
  
  CONCLUSIONS
  In exceptionally short or tall children, the dependency of the SH/H ratio (SDS) on height SDS has to be taken into consideration in the evaluation of body proportions. The sensitivity of the cut-off lines for hypochondroplasia is fair.
authors.affiliation: Department of Paediatrics, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: A M
authors.initials: AM
authors.lastname: Fredriks
authors.forename: S
authors.initials: S
authors.lastname: van Buuren
authors.forename: W J M
authors.initials: WJ
authors.lastname: van Heel
authors.forename: R H M
authors.initials: RH
authors.lastname: Dijkman-Neerincx
authors.forename: S P
authors.initials: SP
authors.lastname: Verloove-Vanhorick
authors.forename: J M
authors.initials: JM
authors.lastname: Wit
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000886:Anthropometry; D001827:Body Height; D001847:Bone Diseases / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D018568:Crown-Rump Length; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007866:Leg / Q000033:anatomy & histology; D008297:Male; D008382:Marfan Syndrome / Q000503:physiopathology; D009426:Netherlands; D011187:Posture; D012016:Reference Values; D012044:Regression Analysis