title: Paediatric reference values for the C-terminal fragment of fibroblast-growth factor-23, sclerostin, bone-specific alkaline phosphatase and isoform 5b of tartrate-resistant acid phosphatase.
abstract: BACKGROUND
  Paediatric reference values for novel markers of phosphate homeostasis, bone formation and resorption and their putative relationship to growth are lacking.
  
  
  METHODS
  A total of 424 healthy children, adolescents and young adults (221 males) aged 0.1-21 y, were enrolled in this cross-sectional study. Height, weight and height velocity were assessed. Plasma/serum samples for determination of C-terminal fragment of fibroblast growth factor-23 (cFGF-23), sclerostin, bone alkaline phosphatase (BAP) and tartrate-resistant acid phosphatase 5b (TRAP5b) were available from 222, 264, 352 and 338 individuals, respectively. Calculation of cross-sectional centiles and z-scores was based on median (M), standard coefficient of variation (S) and the Box-Cox power (L) of transformation (LMS method) per age cohort. Correlations between variables as well as with growth were assessed.
  
  
  RESULTS
  cFGF-23, BAP and TRAP5b were significantly correlated with age (each P < 0.01), with highest values during infancy and adolescence. Serum levels of BAP and TRAP5b were significantly higher in adolescent boys compared with girls (each P < 0.01). In contrast, sclerostin levels were independent of age and gender. BAP and TRAP5b were strongly correlated and both were significantly associated with cFGF-23 and sclerostin as well (each P < 0.01). cFGF-23 was positively correlated with serum phosphate and renal phosphate threshold concentration (each P < 0.01). Height, weight, body mass index and height velocity were weakly correlated with BAP and TRAP5b (each P < 0.05).
  
  
  CONCLUSIONS
  This study provides age- and gender-related centile charts and z-scores for cFGF-23, BAP, TRAP5b and sclerostin and highlights the link between phosphate homeostasis and markers of bone metabolism during growth.
authors.affiliation: Department of Pediatrics, University Children's Hospital Rostock, Ernst-Heydemann-Str. 8, Rostock, Germany. dagmar-christiane.fischer@med.uni-rostock.de
authors.forename: Dagmar-Christiane
authors.initials: DC
authors.lastname: Fischer
authors.forename: Anne
authors.initials: A
authors.lastname: Mischek
authors.forename: Sabrina
authors.initials: S
authors.lastname: Wolf
authors.forename: Anja
authors.initials: A
authors.lastname: Rahn
authors.forename: Birgit
authors.initials: B
authors.lastname: Salweski
authors.forename: Guenther
authors.initials: G
authors.lastname: Kundt
authors.forename: Dieter
authors.initials: D
authors.lastname: Haffner
mesh_terms: D000135:Acid Phosphatase / Q000097:blood* / Q000652:urine; D048868:Adaptor Proteins, Signal Transducing; D000293:Adolescent; D000367:Age Factors; D000469:Alkaline Phosphatase / Q000097:blood* / Q000737:chemistry; D019485:Bone Morphogenetic Proteins / Q000097:blood* / Q000652:urine; D001842:Bone and Bones / Q000737:chemistry*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood* / Q000652:urine; D005819:Genetic Markers; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007527:Isoenzymes / Q000097:blood* / Q000652:urine; D008297:Male; D010372:Pediatrics / Q000706:statistics & numerical data; D020033:Protein Isoforms / Q000097:blood / Q000737:chemistry; D012015:Reference Standards; D012737:Sex Factors; D000071681:Tartrate-Resistant Acid Phosphatase; D055815:Young Adult
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; D007527:Isoenzymes; D020033:Protein Isoforms; C422903:SOST protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase