Metrological traceability in mass spectrometry-based targeted protein quantitation: A proof-of-principle study for serum apolipoproteins A-I and B100

In this study, we have followed up on previous liquid chromatography (LC) multiple reaction monitoring (MRM) mass spectrometry (MS) approaches for measurement of apolipoprotein (apo) A-I and apo B100 in serum aiming for implementation of a multiplexed assay in a clinical chemistry laboratory with full metrological traceability. Signature peptides were selected and detected by dynamic MRM, and stable isotope labeled (SIL)-peptides were used as internal standards. Five apo A-I and four apo B100 peptides were measured in serum digests with linearity (R-2 > 0.992) in the physiologically relevant concentration ranges. Linearity with regard to protein concentration was ascertained at five concentration levels (R-2 > 0.926 and R-2 > 0.965, for the apo A-I and apo 13100 peptides, respectively). Three native value-assigned sera were used as external calibrators for further method verification. Imprecision values on sample preparation and LC-MS/MS acquisition were below the established minimal specifications for apo A-I and apo B100 (5.0% and 5.3%, respectively). Correlation of LC-MS/MS results with immunoturbidimetric assay results, for normo- and hypertriglyceridemic samples, showed R-2 > 0.944 for apo A-I and R-2 > 0.964 for apo B100. This LC-MS/MS method has potential for clinical application in normo- and dyslipidemic patients. (C) 2014 Elsevier B.V. All rights reserved.