A distributable LC-MS/MS method for the measurement of serum thyroglobulin
Junyan Shi, William S. Phipps, Benjamin Y. Owusu, Clark M. Henderson, Thomas J. Laha, Jessica O. Becker, Morteza Razavi, Michelle A. Emrick, Andrew N. Hoofnagle
Abstract
Background: Despite its clear advantages over immunoassay-based testing, the measurement of serum thyroglobulin by mass spectrometry remains limited to a handful of institutions. Slow adoption by clinical laboratories could reflect limited accessibility to existing methods that have sensitivity comparable to modern immunoassays, as well as a lack of tools for calibration and assay harmonization. Methods: We developed and validated a liquid chromatography-tandem mass spectrometry-based assay for the quantification of serum thyroglobulin. The protocol combined peptide immunoaffinity purification using a commercially available, well-characterized monoclonal antibody and mobile phase modification with dimethylsulfoxide (DMSO) for enhanced sensitivity. To facilitate harmonization with other laboratories, we developed a novel, serum-based 5-point distributable reference material (Husky Ref). Results: The assay demonstrated a lower limit of quantification of 0.15 ng/mL (<20 %CV). Mobile phase DMSO increased signal intensity of the target peptide at least 3-fold, improving quantification at low concentrations. Calibration traceable to Husky Ref enabled harmonization between laboratories in an interlaboratory study. Conclusions: Sensitive mass spectrometry-based thyroglobulin measurement can be achieved using a monoclonal antibody during peptide immunoaffinity purification and the addition of mobile phase DMSO. Laboratories interested in deploying this assay can utilize the provided standard operating procedure and freely-available Husky Ref reference material.