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Apolipoprotein F (APO-F) is a novel low abundance liver fibrosis biomarker and its concentration decreases in human serum and plasma across liver fibrosis stages. Currently antibody based assays for APO-F suffer from limitations such as unspecific binding, antibody availability and undetectable target if the protein is degraded; and so an antibody-free assay has the potential to be a valuable diagnostic tool. We report an antibody-free, rapid, sensitive, selective and robust LC-MS/MS (MRM and MRM3) method for the detection and quantitation of APO-F in healthy human plasma. With further analysis of clinical samples, this LC-MS based method could be established as the first ever antibody-free biomarker assay for liver fibrosis. We explain the use of Skyline software for peptide selection and the creation of a reference library to aid in true peak identification of endogenous APO-F peptides in digests of human plasma without protein or peptide enrichment. Detection of a glycopeptide using MRM-EPI mode and reduction of interferences using MRM3 are explained. The amount of APO-F in human plasma from a healthy volunteer was determined to be 445.2 ng/mL, the coefficient of variation (CV) of precision for 20 injections was <12% and the percentage error of each point along the calibration curve was calculated to be <8%, which is in line with the assay requirements for clinical samples.

Original publication

DOI

10.1016/j.jchromb.2016.08.038

Type

Journal article

Journal

Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences

Publisher

Elsevier

Publication Date

15/10/2016