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Uric acid is a precipitating factor for gout and renal disease, and regular monitoring of uric acid concentration is essential for health management. Hence, accurate measurement is indispensable for clinical diagnosis. Reference measurement procedure (RMP) is an essential element to ensure accuracy and comparability of tested results. In this study, the optimization of a candidate RMP (cRMP) adopting isotope dilution coupled with liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) method for human serum uric acid measurement has been developed. The accuracy of this cRMP was validated by measuring certified reference materials (CRMs) and participating in the external quality assessment (EQA) scheme initiated by International Federation of Clinical Chemistry (IFCC) and National Center for Clinical Laboratory (NCCL). Biases were −0.64-1.51%, which were within the required equivalent limit. Excellent precision was obtained with intra- and inter-assay CVs of 0.42–0.73% and 0.20–0.43%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) was determined to be 0.24 and 1.19 μmol/L, respectively. A good liner response was obtained ranged from 30.0 to 895 μmol/L. Compared with the previous RMP for uric acid, the much easier one-step protein precipitation method without further evaporation, the simplified isocratic elution of chromatographic separation condition, and the shorter analysis running time in only 5 min allowed simpler and faster analysis. Moreover, this optimized cRMP was also applied for value assignment for clinical serum samples covered a wide concentration range of uric acid and obtained a decent calibration and measurement capability (CMC). [Display omitted] • The optimization of a candidate RMP (cRMP) adopting ID-LC-MS/MS method for serum uric acid measurement has been developed. • The method performance was fully validated. • The method was applied to clinical samples and compared with routine methods. [ABSTRACT FROM AUTHOR]

We developed and evaluated two-level, namely 2017011 and 2017012, serum-based reference materials (RMs) for 17 beta-estradiol (17 β-E2) by the reference method of isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) from the remaining serum samples after routine clinical tests, to help improve clinical routine testing and provide the traceability of results. This paper describes the development process of these RMs. The National Metrology Institute of Japan (NMIJ) certified reference material (CRM) 6004-a was used as the primary RM for the measurement of 17 β-E2. These serum-based RMs showed satisfactory homogeneity and stability. They also assessed the commutability between the reference method and the three routine clinical immunoassay systems. Besides, a collaborative study was carried out in five reference laboratories, all of which had been accredited by the China National Accreditation Service for Conformity Assessment (CNAS) in accordance with ISO/WD 15725-1. Statistical analysis of raw results and uncertainty assessment obtained certified values: 2017011 was 445.2 ± 39.0 pmol/L, and 2017012 was 761.9 ± 35.5 pmol/L. [ABSTRACT FROM AUTHOR]