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Endocrinology and Metabolism |
1 Northwest Lipid Metabolism and Diabetes Research Laboratory, University of Washington, Seattle, WA.
2 LINCO Diagnostic Services, St. Charles MO.
3 B2S Consulting, Beech Grove, IN.
4 Department of Pathology, Virginia Commonwealth University, Richmond, VA.
5 National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD.
6 Division of Laboratory Services, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA.
7 American Diabetes Association, Alexandria, VA.
8 Department of Laboratory Medicine and Pathology, Medical School, University of Minnesota, Minneapolis, MN.
aAddress correspondence to this author at: Department of Laboratory Medicine and Pathology, Medical School, University of Minnesota, Minneapolis, MN. Fax 612-273-3489; e-mail steff001{at}umn.edu.
Background: Circulating insulin concentration in serum or plasma provides important information for the estimation of insulin secretion and insulin resistance. Currently, lack of standardization of insulin assays hinders efforts to achieve consistent measures for treatment guidelines.
Methods: A Workgroup convened by the American Diabetes Association evaluated 12 different commercial insulin methods from 9 manufacturers.
Results: The within-assay CVs ranged from 3.7% to 39.0%, with 7 of 10 assays having a CV 
10.6%. The among-assay CVs ranged from 12% to 66%, with a median value of 24%. A common insulin reference preparation did not change the among-assay CV and failed to improve harmonization of results among assays. Results from 6 of 10 assays agreed within the total error of 32% that is allowable based on biological variability criteria. Seven of 10 assays recovered insulin added to a serum pool within 15.5% of the expected concentration. In 9 of 10 methods, there was <2% cross-reactivity with intact human proinsulin, and 8 of 10 methods had <3% cross-reactivity with split (32, 33) proinsulin. For 9 of 10 assays, the cross-reactivity of des (64, 65) proinsulin exceeded 40%. Overall, most assays had acceptable imprecision and specificity for insulin.
Conclusion: The discordance in test results for commercial insulin reagent sets is likely multifactorial and will require a continuing effort to understand the differences and achieve the desired consistency and harmonization among commercial immunoassays.
The following articles in journals at HighWire Press have cited this article:
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  H. W. Vesper and L. M. Thienpont Traceability in Laboratory Medicine Clin. Chem., June 1, 2009; 55(6): 1067 - 1075. [Abstract] [Full Text] [PDF]
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W. G. Miller, L. M. Thienpont, K. Van Uytfanghe, P. M. Clark, P. Lindstedt, G. Nilsson, M. W. Steffes, and for the Insulin Standardization Work Group Toward Standardization of Insulin Immunoassays Clin. Chem., May 1, 2009; 55(5): 1011 - 1018. [Abstract] [Full Text] [PDF]
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P. E.M. De Pauw, I. Vermeulen, O. C. Ubani, I. Truyen, E. M.F. Vekens, F. T. van Genderen, J. W. De Grijse, D. G. Pipeleers, C. Van Schravendijk, and F. K. Gorus Simultaneous Measurement of Plasma Concentrations of Proinsulin and C-Peptide and Their Ratio with a Trefoil-Type Time-Resolved Fluorescence Immunoassay Clin. Chem., December 1, 2008; 54(12): 1990 - 1998. [Abstract] [Full Text] [PDF]
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 J. Cacho, J. Sevillano, J. de Castro, E. Herrera, and M. P. Ramos Validation of simple indexes to assess insulin sensitivity during pregnancy in Wistar and Sprague-Dawley rats Am J Physiol Endocrinol Metab, November 1, 2008; 295(5): E1269 - E1276. [Abstract] [Full Text] [PDF]
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 S. E. Manley, S. D. Luzio, I. M. Stratton, T. M. Wallace, and P. M.S. Clark Preanalytical, Analytical, and Computational Factors Affect Homeostasis Model Assessment Estimates Diabetes Care, September 1, 2008; 31(9): 1877 - 1883. [Abstract] [Full Text] [PDF]
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D. Rodriguez-Cabaleiro, K. Van Uytfanghe, V. Stove, T. Fiers, and L. M. Thienpont Pilot Study for the Standardization of Insulin Immunoassays with Isotope Dilution Liquid Chromatography/Tandem Mass Spectrometry Clin. Chem., August 1, 2007; 53(8): 1462 - 1469. [Abstract] [Full Text] [PDF]
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R. Sapin Insulin Immunoassays: Fast Approaching 50 Years of Existence and Still Calling for Standardization Clin. Chem., May 1, 2007; 53(5): 810 - 812. [Full Text] [PDF]
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