PB0086 - Factor V and VII assay discrepancies in the UK NEQAS Blood Coagulation (BC) programme – comparison with International Society on Thrombosis and Haemostasis (ISTH) SSC plasma standard results

Background: The International Society on Thrombosis and Haemostasis (ISTH) SSC plasma standard, calibrated for a range of haemostatic parameters is primarily available to diagnostic manufacturers to aid in labelling commercial plasma. It is also available to EQA providers, to troubleshoot calibration issues for individual centres, and as an EQA sample in routine surveys. UK NEQAS BC exercises had demonstrated discrepant results between users of different reagents for FV and FVII assays.

Aims: Independent confirmation of such discrepancies with the SSC plasma standard may help clarify the source of discrepancy.

Methods: SSC plasma standard lot #5 was distributed to 241 centres performing FV and FVII assays. Results were analysed by reagent, deficient plasma and reference plasma source. The pattern of results was compared to previously distributed UK NEQAS BC samples.

Results: Table 1 shows median results for each method for FV assays and, for comparison, data from a previous NEQAS exercise. Results with reagent B were significantly higher (p < 0.001) than reagents A and C with the SSC plasma standard and also with previous NEQAS plasma samples. The same pattern was observed for reference plasmas, and also deficient plasmas from the same sources. Table 2 shows results for FVII assays. Again results with reagent B were significantly higher (p < 0.001) than those for reagents A and C with the SSC plasma standard. However a previous NEQAS sample (median 26.3IU/dL) showed results with reagents B and C to be in better agreement. The large majority of centres employ reagent, deficient plasma and reference plasma from the same commercial source, making it difficult to identify the source of discrepancies.

Conclusion(s): Compared to the values assigned to the SSC plasma standard, the overall median results for FV and FVII assays in the NEQAS exercise were very close. Exercise such as this can help confirm between-method issues with these assays.