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Table. 5.

Table. 5.

Examples of reasons for sample re-analysis

Observation Re-analysis of patient samples

Incidence (sample or batch) Action Notes
Sample Re-extraction on dilution See “Dilution” section for re-injection options
Carryover Sample Blanks prior to re-analysis to confirm system cleanliness Beware of well-to-well contamination with certain auto- samplers or exceptionally high concentration samples
Carryover Batch Equipment maintenance Root cause may be associated with extraction equipment
QC failure Batch Root-cause analysis to determine origin Use of ISs generally precludes meaningful QC value change on re-injection
Chromatographic degradation/failure Batch Root-cause analysis to determine origin Ensure stability and volume of extracts prior to re-injection
Low response Batch Root-cause analysis to determine origin Any re-injections after repairs must be within the post- extraction stability limits
Failed calibration curve Batch If instrument response is not the root cause, re-preparation of batch is most likely outcome Multiple calibration points must not be rejected to achieve acceptable curve or QC accuracy
Persistent interference Batch Re-injection on reflex method Evaluate frequency to determine need for exclusively utilizing the reflex method
Transition ratio failure Sample Re-extraction on dilution or reflex method
IS recovery Sample Re-extraction on dilution or reflex method Very high analyte concentrations may inhibit ionization of the IS
IS recovery Batch Root-cause determines re-extraction (error in sample preparation) or re-injection (error in instrumentation) Any re-injections after repairs must be within the post- extraction stability limits
Retention time shift Sample If re-injection is insufficient, dilution on re- extraction or reflex method Pressure trace associated with sample may indicate acute liquid-flow issue
Retention time shift Batch LC troubleshooting to determine root-cause

Abbreviations: LC, liquid chromatography; QC, quality control; IS, internal standard.

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

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