Averaging of results derived from different, simultaneously acquired mass transitions in ID-LC-MS/MS - Potential impact on measurement imprecision.

Background: LC-MS/MS allows for many measurands monitoring different mass transitions simultaneously. So far, such alternative mass transitions are usually assessed as "quantifier and qualifier ions" in order to rule out interferences in individual samples. However, quantification can also be based on assessment of alternative mass transitions for both the measurand and its internal standard, with two distinct results for one injection of an individual sample. These paired results can be averaged. The aim of this study was to determine the potential impact of this averaging approach on measurement imprecision.

Methods: We studied the impact of averaging results from different transitions for four exemplary measurands (linezolid (LIN), piperacillin (PIP), voriconazole (VOR), ethylglucuronide (ETG)). Intra-batch studies were performed with 21 injections of single clinical samples in sequence for each analyte (LIN, PIP, VOR), and a between-batch study with evaluation of data from routine QC samples from 20 series over 20 weeks (ETG). CVs and their confidence intervals were assessed comparatively for quantification based on single transitions, and for averaged results from these two transitions, respectively.

Results: In all data sets, we observed lower CVs for the averaged results compared to the results obtained from single mass transitions. CVs from averaged results were up to 39.4% lower compared to the CVs observed for results obtained from single transitions for the respective measurands.

Conclusion: Averaging of quantification results obtained from separate mass transitions acquired simultaneously in ID-LC-MS/MS seems to have the potential to minimize the measurement imprecision for different measurands in short- and long-term settings.