A Mass-Spectrometry-Based Antibody-Free Approach Enables the Quantification of D‑Dimer in Plasma

D-dimer
is an important marker of different coagulation diseases,
such as venous thromboembolism (including deep vein thrombosis and
pulmonary embolism) and disseminated intravascular coagulation. Though
it is frequently used in many clinical diagnostic situations, the
D-dimer assays currently lack standardization due to its inherent
heterogeneity which makes the antibody-based methods have different
quantitative results and cutoffs to define an abnormal value. In this
study, we report the first antibody-free D-dimer quantification method.
In the method, a cross-linked peptide of fibrin D domain carboxyl
terminal cross-linked by the factor XIIIa was used to represent the
D-dimer. By using a filter-aided sample preparation and a nickel immobilized
metal affinity chromatography enrichment strategy, the complexity
of the plasma sample was significantly reduced, and the cross-linked
peptide was enriched effectively for analysis with parallel reaction
monitoring in mass spectrometry. The linear range of this method was
3.125–400 nmol/L which spans over two magnitudes. Recovery
and reproducibility of the method were found to be good. To further
demonstrate the performance of our method, D-dimer concentrations
of 25 human plasma samples were analyzed, and the results had a good
correlation between with the commercial D-dimer assay kit used in
hospitals. This method was completely antibody-free and has the potential
to promote the standardization of D-dimer analysis.