title: Evaluation of an automated soluble transferrin receptor (sTfR) assay on the Roche Hitachi analyzer and its comparison to two ELISA assays.
abstract: BACKGROUND
  Soluble transferrin receptor (sTfR) assays are currently not standardized. This hinders data comparison between studies and also affects the use of a recently proposed model to estimate body iron.
  
  
  METHODS
  We evaluated the analytical performance of a fully automated sTfR immunoturbidimetric assay (Roche Diagnostics) and compared it with two ELISA assays (Ramco Laboratories and an in-house ELISA assay used in the body iron model).
  
  
  RESULTS
  The Roche assay showed excellent intra- and inter-assay precision (CV<5%). Prolonged exposure of serum samples to room temperature and multiple freeze-thaw cycles did not affect sTfR concentrations. Receiver-operator characteristic curve analysis demonstrated that the Roche assay (area-under-the-curve (AUC)=0.882) was superior to the Ramco assay (AUC=0.794) in predicting iron deficiency (defined as serum ferritin <10 microg/L; P=0.013). Method comparison between the Roche and the two ELISA assays showed good correlations (r>0.8); however, sTfR values by the Roche assay were on average 30% lower than values obtained with the two ELISA assays.
  
  
  CONCLUSIONS
  sTfR data measured with an immunoturbidimetric assay can be compared to a commonly used ELISA assay, and can be used in the body iron model through regression equations obtained in the present study.
authors.affiliation: Centers for Disease Control and Prevention, National Center for Environmental Health, Atlanta, GA 30345, USA. cpfeiffer@cdc.gov
authors.forename: Christine M
authors.initials: CM
authors.lastname: Pfeiffer
authors.forename: James D
authors.initials: JD
authors.lastname: Cook
authors.forename: Zuguo
authors.initials: Z
authors.lastname: Mei
authors.forename: Mary E
authors.initials: ME
authors.lastname: Cogswell
authors.forename: Anne C
authors.initials: AC
authors.lastname: Looker
authors.forename: David A
authors.initials: DA
authors.lastname: Lacher
mesh_terms: D001331:Automation; D019963:Clinical Chemistry Tests / Q000295:instrumentation*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation*; D012372:ROC Curve; D011933:Reagent Kits, Diagnostic; D011990:Receptors, Transferrin / Q000097:blood*; D015203:Reproducibility of Results
chemical_list: D011933:Reagent Kits, Diagnostic; D011990:Receptors, Transferrin