BACKGROUND: Our purpose was to establish a mass spectrometry reference measurement procedure (RMP) for cholesterol to use in the CDC's standardization programs. We explored a gas chromatography-isotope dilution mass spectrometry (GC-IDMS) procedure using a multilevel standard calibration curve to quantify samples with varying cholesterol concentrations. METHODS: We calibrated the mass spectrometry instrument by isotope dilution with a pure primary standard reference material and an isotopically enriched cholesterol analog as the internal standard (IS). We diluted the serum samples with Tris-HCl buffer (pH 7.4, 0.05 mol/L, 0.25% Triton X-100) before analysis. We used 17 serum pools, 10 native samples, and 2 standard reference materials (SRMs). We compared the GC-IDMS measurements with the CDC's modified Abell-Levy-Brodie-Kendall (AK) RMP measurements and assessed method accuracy by analyzing 2 SRMs. We evaluated the procedure for lack of interference by analyzing serum spiked with a mixture of 7 sterols. RESULTS: The mean percent bias between the AK and the GC-IDMS RMP was 1.6% for all samples examined. The mean percent bias from NIST's RMP was 0.5% for the SRMs. The total %CVs for SRM 1951b levels I and II were 0.61 and 0.73%, respectively. We found that none of the sterols investigated interfered with the cholesterol measurement. CONCLUSIONS: The low imprecision, linear response, lack of interferences, and acceptable bias vs the NIST primary RMP qualifies this procedure as an RMP for determining serum cholesterol. The CDC will adopt and implement this GC-IDMS procedure for cholesterol standardization.
BACKGROUND: Our purpose was to establish a mass spectrometry reference measurement procedure (RMP) for cholesterol to use in the CDC's standardization programs. We explored a gas chromatography-isotope dilution mass spectrometry (GC-IDMS) procedure using a multilevel standard calibration curve to quantify samples with varying cholesterol concentrations. METHODS: We calibrated the mass spectrometry instrument by isotope dilution with a pure primary standard reference material and an isotopically enriched cholesterol analog as the internal standard (IS). We diluted the serum samples with Tris-HCl buffer (pH 7.4, 0.05 mol/L, 0.25% Triton X-100) before analysis. We used 17 serum pools, 10 native samples, and 2 standard reference materials (SRMs). We compared the GC-IDMS measurements with the CDC's modified Abell-Levy-Brodie-Kendall (AK) RMP measurements and assessed method accuracy by analyzing 2 SRMs. We evaluated the procedure for lack of interference by analyzing serum spiked with a mixture of 7 sterols. RESULTS: The mean percent bias between the AK and the GC-IDMS RMP was 1.6% for all samples examined. The mean percent bias from NIST's RMP was 0.5% for the SRMs. The total %CVs for SRM 1951b levels I and II were 0.61 and 0.73%, respectively. We found that none of the sterols investigated interfered with the cholesterol measurement. CONCLUSIONS: The low imprecision, linear response, lack of interferences, and acceptable bias vs the NIST primary RMP qualifies this procedure as an RMP for determining serum cholesterol. The CDC will adopt and implement this GC-IDMS procedure for cholesterol standardization.
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Authors: Dieter Lütjohann; Ingemar Björkhem; Silvia Friedrichs; Anja Kerksiek; Anita Lövgren-Sandblom; Wolf-Jochen Geilenkeuser; Robert Ahrends; Isabel Andrade; Diana Ansorena; Iciar Astiasarán; Lucía Baila-Rueda; Bianca Barriuso; Susen Becker; Lionel Bretillon; Richard W Browne; Claudio Caccia; Uta Ceglarek; Ana Cenarro; Peter J Crick; Günter Fauler; Guadalupe Garcia-Llatas; Robert Gray; William J Griffiths; Helena Gylling; Scott Harding; Christin Helmschrodt; Luigi Iuliano; Hans-Gerd Janssen; Peter Jones; Leena Kaipiainen; Frank Kannenberg; María Jesús Lagarda; Valerio Leoni; Ana Maria Lottenberg; Dylan S MacKay; Silke Matysik; Jeff McDonald; Maria Menendez-Carreño; Semone B Myrie; Valéria Sutti Nunes; Richard E Ostlund; Eliana Polisecki; Fernando Ramos; Todd C Rideout; Ernst J Schaefer; Gerd Schmitz; Yuqin Wang; Chiara Zerbinati; Ulf Diczfalusy; Hans-Frieder Schött Journal: J Steroid Biochem Mol Biol Date: 2019-03-30 Impact factor: 4.292