Simple procedures can markedly enhance automated immunoassay performance.

Theoretically, optimal performance for an immunoassay system is achieved when both the interassay and within-run precisions are identical. Using the Ciba Corning ACS:180 automated immunoassay system, the authors made two simple changes to the operating procedures that allowed near-optimal analytic performance (as assessed with the interassay coefficient of variation determined by the protocol of the National Committee for Clinical Laboratory Standards) for four of six hormones: thyroid-stimulating hormone, luteinizing hormone, prolactin, and human chorionic gonadotropin. At low hormone concentrations, the 20% interassay coefficients of variation for the hormones assayed were as follows: free tetraiodothyronine, 1.74 pM; thyroid-stimulating hormone, .033 mIU/L; luteinizing hormone, .21 U/L; follicle-stimulating hormone, .69 U/L; prolactin, 5.03 mU/L; and human chorionic gonadotropin, 1.52 mU/L. The operational enhancements improved the analytic performance of the assay for all hormones assessed compared with the performance of previously used isotopic immunoassays.