title: Determination of serum and plasma sclerostin concentrations by enzyme-linked immunoassays.
abstract: BACKGROUND
  Sclerostin alters bone formation. The precise and reproducible measurement of sclerostin concentrations in biological samples is important for assessment of metabolic bone disease. We determined sclerostin concentrations in serum and plasma using two commercially available ELISA.
  
  
  METHODS
  We measured sclerostin concentrations in serum or heparin-plasma obtained from 25 normal human subjects using two commercial ELISA available from Biomedica Medizinprodukte GmbH and TECOmedical AG.
  
  
  RESULTS
  With the Biomedica assay, serum sclerostin concentrations were 0.99 ± 0.12 ng/ml (mean ± sem), and plasma concentrations were 1.47 ± 0.13 ng/ml (paired t test, P < 0.001). With the TECO assay, serum sclerostin levels were 0.71 ± 0.05 ng/ml, and plasma sclerostin concentrations were 0.80 ± 0.06 ng/ml (paired t test, P < 0.001). Serum and plasma sclerostin concentrations were significantly different when determined by the two assays (serum, P = 0.015; plasma, P < 0.001). Recovery of added recombinant sclerostin to serum was less than expected with both Biomedica and TECO assays (P < 0.001, paired t test).
  
  
  CONCLUSIONS
  The concentrations of sclerostin in serum and plasma are different when determined by the two assays. Serum or plasma sclerostin concentrations with current assays should be interpreted with caution. The data suggest that the same assay should be used for comparing groups of patients or patients being followed longitudinally. Standardization of sclerostin assays is required before being introduced into general clinical laboratory use.
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: McNulty
authors.forename: Ravinder J
authors.initials: RJ
authors.lastname: Singh
authors.forename: Xujian
authors.initials: X
authors.lastname: Li
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Bergstralh
authors.forename: Rajiv
authors.initials: R
authors.lastname: Kumar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D019485:Bone Morphogenetic Proteins / Q000097:blood*; D005260:Female; D005819:Genetic Markers; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; C422903:SOST protein, human