title: Comparison of immunoassays for the selective measurement of human high-molecular weight adiponectin.
abstract: BACKGROUND
  Adiponectin is an adipocyte-derived hormone circulating in different multimer complexes. The high-molecular-weight (HMW) complex is likely the active form of this protein and has been recognized as a risk marker for type 2 diabetes and coronary artery disease (CAD). Because quantification of HMW adiponectin by Western blot analysis is time-consuming, novel ELISAs have been developed to simplify measurements in clinical research. However, these enzyme immunoassays have not been cross-validated in larger patient groups. We evaluated 2 individual ELISA systems by comparison to Western blotting for measurement of the distribution of HMW adiponectin in healthy individuals and patients with CAD and type 2 diabetes.
  
  
  METHODS
  We measured HMW adiponectin in 204 individuals (83 CAD patients, 81 type 2 diabetes patients, and 40 healthy controls). Correlations, range of agreement, and imprecision of HMW concentrations obtained using 2 commercial ELISAs (#1, ALPCO Diagnostics; #2, Millipore) were evaluated by comparison with quantitative Western blotting.
  
  
  RESULTS
  Adiponectin results of the ELISAs were significantly correlated with those obtained by Western blotting (both r > 0.75, P < 0.001). Deming regression and Bland-Altman analyses indicated high agreement among the 3 immunoassays. The median difference between HMW adiponectin concentrations measured by ELISA and by Western blot was +0.4 mg/L for ELISA #1 and -0.4 mg/L for ELISA #2 with 95% of value differences <3 mg/L.
  
  
  CONCLUSIONS
  Selective measurement of HMW adiponectin by ELISA is feasible; however, individual differences among immunoassays must be considered. The evaluated ELISAs exhibit analytical characteristics that allow their use as equivalent for Western blot analysis in larger clinical and epidemiological groups.
authors.affiliation: Department of Nephrology, Technische Universitaet Muenchen, Munich, Germany.
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.forename: Tibor
authors.initials: T
authors.lastname: Schuster
authors.forename: Marcus
authors.initials: M
authors.lastname: Baumann
authors.forename: Marcel
authors.initials: M
authors.lastname: Roos
authors.forename: Daniel
authors.initials: D
authors.lastname: Sollinger
authors.forename: Jens
authors.initials: J
authors.lastname: Lutz
authors.forename: Uwe
authors.initials: U
authors.lastname: Heemann
authors.forename: Maximilian
authors.initials: M
authors.lastname: von Eynatten
mesh_terms: D052242:Adiponectin / Q000097:blood / Q000276:immunology; D016022:Case-Control Studies; D003324:Coronary Artery Disease / Q000097:blood / Q000276:immunology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000276:immunology; D006262:Health; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008970:Molecular Weight
chemical_list: C499918:ADIPOQ protein, human; D052242:Adiponectin