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Table. 4.

Table. 4.

Examples of data metrics and method of review for LC-MS/MS assays

Post-analytical data component Check
IS recovery–sample Plot or percentages compared to knowns (calls, QCs)
IS recovery–batch Plot or linear regression
Retention times Plot or linear regression
Transition ratio Compared to expected ratio from knowns (calibrators/QCs)
Calibration curve–fit High calibrator with lower % accuracy in a linear fit indicates quadratic best-fit. May be due to extraction, source saturation, or detector blinding
Calibration curve–outliers Gross outliers (accuracy outside of 85–115/80%–120%)
Calibration curve–regression equation between batches Large changes in slope or intercept may indicate need for troubleshooting
QCs–acute accuracy QCs within 15% of expected concentration or tighter criteria based on assay requirements
QCs–precision (Westgard) QCs reviewed based on Westgard rules*
Carryover–high standard to blank Establishes expectation of carryover within the batch
Critical values Concentrations with a defined threshold are immediately reported to the physician
Blank contamination Contribution of IS to analyte
Double blank contamination Contribution of procedure to IS response
Carryover–samples Samples greater than carryover limit reviewed/reinjected

*QC review by Westgard rules for multianalyte panels may be difficult to apply. See section “Operation of LC-MS/MS assays.”

Abbreviations: LC-MS/MS, liquid chromatography-tandem mass spectrometry; IS, internal standard; QC, quality control.

Ann Lab Med 2022;42:531~557 https://doi.org/10.3343/alm.2022.42.5.531

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