Comparison of immunoassays for the selective measurement of human high-molecular weight adiponectin.
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.
Liu
Dan
D
Department of Nephrology, Technische Universitaet Muenchen, Munich, Germany.
Schuster
Tibor
T
Baumann
Marcus
M
Roos
Marcel
M
Sollinger
Daniel
D
Lutz
Jens
J
Heemann
Uwe
U
von Eynatten
Maximilian
M
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
C499918:ADIPOQ protein, human; D052242:Adiponectin