Performance evaluation and cross-reactivity from insulin analogs with the ARCHITECT insulin assay

Background: Insulin measurement is used for the diagnosis of hypoglycemia and for insulin pharmacokinetic evaluations. We assessed the analytical and clinical performance of the ARCHITECT insulin assay, a chemiluminescent immunoassay recently introduced for the ARCHITECT i2000 fully automated immunoassay analyzer (Abbott Laboratories). We also tested whether major insulin analogs cross-reacted with the immunoassay reagents. Methods: We used Clinical and Laboratory Standards Institute protocols to assess the analytical performance of the ARCHITECT insulin assay and compared its accuracy with that of the E-test TOSOH II (IRI) from TOSOH Corporation. We used 3 recombinant insulin analogs (lispro, aspart, and glargine) to evaluate the cross-reactivity of insulin analogs with the ARCHITECT immunoassay reagent. Results: The total CV for the ARCHITECT assay was < 5%. Correlation between the ARCHITECT insulin assay and the E-test TOSOH II (IRI) was satisfactory in the measured range, but we detected a slope deviation between the assays. The ARCHITECT insulin assay showed low cross-reactivity to the insulin analog aspart, whereas it detected the other insulin analogs, lispro and glargine, in concentrations as high as the theoretical concentrations. Conclusions: The ARCHITECT insulin assay showed favorable basic performance, including reproducibility, dilution linearity, detection limit, and effects of interfering substances. When interpreting results, clinicians and laboratory pathologists should be aware of the cross-reactivity of the ARCHITECT and other immunoassays to specific insulin analogs prescribed to diabetes patients. (c) 2006 American Association for Clinical Chemistry.