title: Association of kidney function, vitamin D deficiency, and circulating markers of mineral and bone disorders in CKD.
abstract: BACKGROUND
  Vitamin D (25 hydroxyvitamin D [25(OH)D]) deficiency is common in patients with chronic kidney disease (CKD). Neither the relation of this deficiency to the decrease in glomerular filtration rate (GFR) nor the effects on CKD mineral and bone disorders (MBD) are clearly established.
  
  
  METHODS
  Cross-sectional analysis of baseline data from a prospective cohort, the NephroTest Study.
  
  
  METHODS
  1,026 adult patients with all-stage CKD not on dialysis therapy or receiving vitamin D supplementation.
  
  
  METHODS
  For part 1, measured GFR (mGFR) using (51)Cr-EDTA renal clearance; for part 2, 25(OH)D deficiency at <15 ng/mL.
  
  
  METHODS
  For part 1, 25(OH)D deficiency and several circulating MBD markers; for part 2, circulating MBD markers.
  
  
  RESULTS
  For part 1, the prevalence of 25(OH)D deficiency was associated inversely with mGFR, ranging from 28%-51% for mGFR ≥60-<15 mL/min/1.73 m(2). It was higher in patients of African origin; those with obesity, diabetes, hypertension, macroalbuminuria, and hypoalbuminemia; and during winter. After adjusting for these factors, ORs for 25(OH)D deficiency increased from 1.4 (95% CI, 0.9-2.3) to 1.4 (95% CI, 0.9-2.1), 1.7 (95% CI, 1.1-2.7), and 1.9 (95% CI, 1.1-3.6) as mGFR decreased from 45-59 to 30-44, 15-29, and <15 (reference, ≥60) mL/min/1.73 m(2) (P for trend = 0.02). For part 2, 25(OH)D deficiency was associated with higher age-, sex-, and mGFR-adjusted ORs of ionized calcium level <1.10 mmol/L (2.6; 95% CI, 1.2-5.9), 1,25 dihydroxyvitamin D concentration <16.7 pg/mL (1.8; 95% CI, 1.3-2.4), hyperparathyroidism (1.8; 95% CI, 1.3-2.4), and serum C-terminal cross-linked collagen type I telopeptides concentration >1,000 pg/mL (1.6; 95% CI, 1.0-2.6). It was not associated with hyperphosphatemia (phosphate >1.38 mmol/L).
  
  
  CONCLUSIONS
  Cross-sectional analysis of the data prevents causal inferences.
  
  
  CONCLUSIONS
  25(OH)D deficiency is related independently to impaired mGFR. Both mGFR decrease and 25(OH)D deficiency are associated with abnormal levels of circulating MBD biomarkers.
authors.affiliation: Nephrology Dialysis, Clinique du Landy, Saint Ouen, France.
authors.forename: Pablo
authors.initials: P
authors.lastname: Ureña-Torres
authors.forename: Marie
authors.initials: M
authors.lastname: Metzger
authors.forename: Jean Philippe
authors.initials: JP
authors.lastname: Haymann
authors.forename: Alexandre
authors.initials: A
authors.lastname: Karras
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Boffa
authors.forename: Martin
authors.initials: M
authors.lastname: Flamant
authors.forename: François
authors.initials: F
authors.lastname: Vrtovsnik
authors.forename: Cédric
authors.initials: C
authors.lastname: Gauci
authors.forename: Marc
authors.initials: M
authors.lastname: Froissart
authors.forename: Pascal
authors.initials: P
authors.lastname: Houillier
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Stengel
mesh_terms: D000328:Adult; D017954:Africa South of the Sahara / Q000208:ethnology; D000368:Aged; D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers; D001851:Bone Diseases, Metabolic / Q000097:blood / Q000453:epidemiology*; D002908:Chronic Disease; D015331:Cohort Studies; D024042:Collagen Type I / Q000097:blood; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005602:France / Q000453:epidemiology; D005919:Glomerular Filtration Rate; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood / Q000453:epidemiology; D007668:Kidney / Q000503:physiopathology*; D007674:Kidney Diseases / Q000097:blood / Q000453:epidemiology* / Q000503:physiopathology; D008875:Middle Aged; D008903:Minerals / Q000378:metabolism*; D009961:Orosomucoid / Q000032:analysis; D010455:Peptides / Q000097:blood; D015995:Prevalence; D011446:Prospective Studies; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology*; D014900:West Indies / Q000208:ethnology
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D008903:Minerals; D009961:Orosomucoid; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D000469:Alkaline Phosphatase