Increasing clinical liquid chromatography/tandem mass spectrometry assay throughput using a full calibration curve...

Mass spectrometry (MS) generally delivers more accurate results than immunoassay (IA) for certain clinically relevant analytes, but IA is still the more prevalent methodology used by clinical laboratories because of barriers to MS adoption, such as lower throughput. Therefore, it is increasingly important to develop new strategies to increase LC/MS/MS throughput so that more accurate results can be delivered to patients and clinicians.

Throughput can be increased by reducing assay calibration time using a single-tube calibrator, a mix of isotopologues of the target analyte at different concentrations in a biological matrix, rather than a set of traditional, multiple-tube calibrators. One injection from a single-tube calibrator can generate a full calibration curve such that each calibration point is from the multiple reaction monitoring (MRM) signal corresponding to a specific isotopologue.

In this study, a single-tube calibrator (five levels in one vial) and a set of multiple-tube calibrators (seven levels in seven vials) were used to measure the concentration of testosterone in 42 serum samples originally value assigned by the Centers for Disease Control and Prevention (CDC) reference method. The bias between the CDC reference method and the single-tube calibrator measurements and the multiple-tube calibrators measurements was +1.1% and - 5.5%, respectively. These results were within the CDC Hormone Standardization (HoSt) program bias acceptance criteria of ±6.4%.

The results show that LC/MS/MS throughput can be increased using a single-tube calibrator because it reduces assay calibration time while delivering equivalent results to those generated using traditional, multiple-tube calibrators. The single-tube calibrator may also save cost to laboratories through reductions in consumable consumption, technician labor time, and inventory management, as well as to manufacturers because fewer vials would need to be manufactured, tested, stored, and shipped.