Enhanced detection and Characterization of M-proteins in multiple myeloma patients using An Agilent AssayMAP Bravo liquid handling system coupled to an LC-QTOF

Background

Mass spectrometry methods are emerging as tools to detect M−proteins in the serum of multiple myeloma patients with increased sensitivity and specificity compared to traditional electrophoretic methods.

Methods

A liquid handling system, the Agilent AssayMAP Bravo, with liquid chromatography high-resolution quadrupole-time-of-flight (LC-QTOF) mass spectrometry to analyze intact light chains was compared to immunofixation electrophoresis (IFE) for M−protein analysis. 210 patient serum samples were analyzed in a split sample comparison (LC-QTOF vs. IFE). LC-QTOF and IFE were interpreted by different individuals in a blinded fashion and results were grouped into four categories: IFE+/QTOF+, IFE+/QTOF-, IFE-/QTOF+, or IFE-/QTOF-.

Results

The LC-QTOF method is able to determine the isotype of M−proteins in a similar fashion to IFE. The estimated limit of detection was ∼ 35 mg/L for adalimumab. For split patient samples, 168 were QTOF+/IFE+, 25 were QTOF-/IFE-, 14 were QTOF+/IFE-, and three were QTOF-/IFE + . Excluding the QTOF+/IFE- results due to the improved sensitivity of the LC-QTOF method, the concordance of LC-QTOF with IFE was ∼ 98 %. The LC-QTOF method also offers improved specificity compared to electrophoretic methods due to inclusion of the accurate mass of the light chains.

Conclusions

The LC-QTOF method was deemed fit for clinical use as a qualitative test with increased sensitivity and specificity compared to IFE. The LC-QTOF can also better resolve therapeutic and multiple myeloma IgG-kappa M−proteins, which present a challenge for electrophoretic methods. Future work will determine suitability of this method as an assessment of minimal residual disease status.