title: Determinants of 25(OH)D sufficiency in obese minority children: selecting outcome measures and analytic approaches.
abstract: OBJECTIVE
  To highlight complexities in defining vitamin D sufficiency in children.
  
  
  METHODS
  Serum 25-(OH) vitamin D [25(OH)D] levels from 140 healthy obese children age 6 to 21 years living in the inner city were compared with multiple health outcome measures, including bone biomarkers and cardiovascular risk factors. Several statistical analytic approaches were used, including Pearson correlation, analysis of covariance (ANCOVA), and "hockey stick" regression modeling.
  
  
  RESULTS
  Potential threshold levels for vitamin D sufficiency varied by outcome variable and analytic approach. Only systolic blood pressure (SBP) was significantly correlated with 25(OH)D (r = -0.261; P = .038). ANCOVA revealed that SBP and triglyceride levels were statistically significant in the test groups [25(OH)D <10, <15 and <20 ng/mL] compared with the reference group [25(OH)D >25 ng/mL]. ANCOVA also showed that only children with severe vitamin D deficiency [25(OH)D <10 ng/mL] had significantly higher parathyroid hormone levels (Δ = 15; P = .0334). Hockey stick model regression analyses found evidence of a threshold level in SBP, with a 25(OH)D breakpoint of 27 ng/mL, along with a 25(OH)D breakpoint of 18 ng/mL for triglycerides, but no relationship between 25(OH)D and parathyroid hormone.
  
  
  CONCLUSIONS
  Defining vitamin D sufficiency should take into account different vitamin D-related health outcome measures and analytic methodologies.
authors.affiliation: Division of Pediatric Endocrinology, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
authors.forename: Clyde
authors.initials: C
authors.lastname: Schechter
authors.forename: Ziyong
authors.initials: Z
authors.lastname: Cai
authors.forename: Morri
authors.initials: M
authors.lastname: Markowitz
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism; D002318:Cardiovascular Diseases / Q000378:metabolism; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008913:Minority Groups; D009765:Obesity / Q000097:blood*; D010281:Parathyroid Hormone / Q000378:metabolism; D012044:Regression Analysis; D012107:Research Design; D016896:Treatment Outcome; D014280:Triglycerides / Q000378:metabolism; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D014280:Triglycerides; D014807:Vitamin D