title: Comparison of two commercially available ELISAs for circulating sclerostin.
abstract: This study investigates the performance and correlation of sclerostin measurements by two commercially available sclerostin ELISAs from TECOmedical and Biomedica. We found that the correlation between the results of two sclerostin assays is strong.
  
  
  BACKGROUND
  Circulating sclerostin levels may provide insight into the pathophysiology of metabolic bone diseases such as osteoporosis. However, recent studies suggest that commercially available assays give different results. We compare the analytical performance of the two most used commercially available sclerostin ELISAs from TECOmedical and Biomedica.
  
  
  METHODS
  Sclerostin levels were assessed in 20 paired serum, EDTA, and heparin plasma convenience samples from hospitalized patients. In addition, sclerostin was measured in serum samples from 34 patients with metabolic bone diseases and from 10 patients with chronic kidney disease (CKD). Samples from three healthy donors were used to determine stability and intra- and inter- assay precision.
  
  
  RESULTS
  The average serum sclerostin concentration of all patients (n = 64) was 0.713 ± 0.58 ng/mL with the Biomedica assay and 0.734 ± 0.43 ng/mL with the TECO assay (p < 0.05). The results correlated strongly (r = 0.9; p < 0.0001), with Passing-Bablok regression showing a linear relationship but with a slight systematic and proportional difference between both assays. Sclerostin levels were about 30% higher in plasma than in serum for both assays, while no significant difference was seen between EDTA and heparin plasma. Intra- and inter- precision were <10% for TECO and <20% for Biomedica. Samples were stable for up to three freeze-thaw cycles with both assays.
  
  
  CONCLUSIONS
  The two commercially available ELISAs for measuring circulating levels of sclerostin are comparable. However, given the small but statistically significant systematic and proportional differences between both assays, results and reference ranges will be assay-specific. Results will also be specific to serum or plasma.
authors.affiliation: Department of Medicine, Division of Endocrinology, Metabolic Bone Diseases Unit, College of Physicians and Surgeons, Columbia University, 630 W. 168th St PH 8 West, Room 864, New York, NY, 10032, USA, ac3024@columbia.edu.
authors.forename: A G
authors.initials: AG
authors.lastname: Costa
authors.forename: S
authors.initials: S
authors.lastname: Cremers
authors.forename: E
authors.initials: E
authors.lastname: Dworakowski
authors.forename: M
authors.initials: M
authors.lastname: Lazaretti-Castro
authors.forename: J P
authors.initials: JP
authors.lastname: Bilezikian
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D015415:Biomarkers / Q000097:blood; D001851:Bone Diseases, Metabolic / Q000097:blood*; D019485:Bone Morphogenetic Proteins / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D005819:Genetic Markers; D006801:Humans; D008297:Male; D010024:Osteoporosis / Q000097:blood; D015663:Osteoporosis, Postmenopausal / Q000097:blood; D051436:Renal Insufficiency, Chronic / Q000097:blood; D015203:Reproducibility of Results
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015415:Biomarkers; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; C422903:SOST protein, human