Transferability and Between Laboratory Imprecision of an LC-MS/MS-Based Reference Measurement Procedure for Apolipoproteins.

BACKGROUND

Apolipoprotein standardization in multiple calibration laboratories requires equivalent results to value assign matrix-based reference and external quality assurance materials. A multiplexed LC-MS/MS-based reference measurement procedure (RMP) has been developed for serum apolipoproteins apo(a), apoA-I, apoB, apoC-I, apoC-II, apoC-III, and apoE. This study evaluates the transferability of the RMP between 3 calibration labs and determines the between-laboratory imprecision.

METHODS

Six periodic ring trial surveys were held. The study protocol, calibrators, internal standards, quality controls (QCs), and clinical samples (CSs) were shared among the laboratories. Intra-laboratory imprecision and inter-peptide comparisons evaluated intra-laboratory performance, while inter-laboratory imprecision evaluated equivalence between the calibration labs. Precision of the common bilevel QC monitored the level of harmonization over time.

RESULTS

Intra-laboratory imprecision fulfilled predefined analytical performance, defined as repeatability <50% of the maximum allowable uncertainty (MAU) at minimal criteria. Median interlaboratory variation (CVbl) was 3.71%, 3.33%, 7.38%, 6.74%, 3.88%, and 3.90% for apoA-I, apoB, apoC-I, apoC-II, apoC-III, and apoE, respectively. For apo(a), CVbl was concentration (x) dependent following 206.32×x-0.899%. In QC samples, the average imprecision for all apolipoproteins decreased from 6.0% and 18.1% for QC1 and QC2, to 5.2% and 9.5%, indicating improvement of analytical performance of the network over time.

CONCLUSIONS

This study shows the feasibility of transferring the multiplex apo LC-MS/MS-based RMP between laboratories. Predefined performance specifications were fulfilled for all seven apolipoproteins. Ongoing round-robin studies will ensure stable performance of the calibration labs required to accomplish an accurate value-base for apolipoprotein certification of commercial reagents.