Protease impurities in raw materials used in enzyme immunoassays can impair assay performance. This risk may be greatly decreased if incoming protein-based raw materials are controlled for protease impurities or if protease inhibitors are used in the assay formulations. As many different proteases might occur in protein raw materials, it is desirable to have a general test for protease contamination. With the help of a fluorescence resonance energy transfer peptide library containing about 2.5 million peptides, we have succeeded in establishing such a system, with sensitivity in the nanogram range for known proteases. Protease contamination was found to differ between different raw materials and was correlated with assay performance. Protease activity in contaminated raw materials could be suppressed to various degrees with different chemical inhibitors or by thermal treatment. This technology is suited for the control of incoming protein-based raw materials used for enzyme immunoassays, as well as for the optimization of the use of protein inhibitors or thermal treatment of protein-based raw materials for the inactivation of proteases.

Determination of the concentration of human luteinizing hormone plays an important role for the prediction of ovulation, evaluation of infertility, diagnosis of pituitary and gonadal disorders and in the differential diagnosis of puberty disorders. The ARCHITECT LH chemiluminescent-immunoassay for the quantitative determination of luteinizing hormone in human serum and plasma serves this clinical utility. The assay was redesigned to improve robustness in terms of better lot-to-lot consistency, allowing users to discontinue current practice of matching reagent, calibrators and controls. The redesigned ARCHITECT LH assay was evaluated on the ARCHITECT instrument-platform and compared to the predicate device: the previously marketed ARCHITECT LH assay. Total imprecision of the assay was 2.4-8.9%CV across the claimed measuring interval (0.09-250.00 mIU/mL). Detection Limits were determined as Limit of Quantitation with 0.09 mIU/mL, Limit of Blank 0.01 mIU/mL and Limit of Detection 0.03 mIU/mL. Correlation slope to the predicate ARCHITECT LH assay was 1.04. Linearity was demonstrated in the claimed measuring interval. Mean recovery was determined to be 101.0 %. Process capability indices demonstrated excellent (>6 Sigma) lot-to-lot reproducibility. The redesigned ARCHITECT LH assay showed excellent performance and good correlation to the predicate device. The high lot-to-lot reproducibility demonstrates excellent process capability and allows more flexibility in managing inventory for end-users. Matching of reagents, calibrators and controls is no longer required. The ARCHITECT LH assay is a valuable tool in clinical laboratories for the accurate and precise quantitation of human luteinizing hormone.

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