Introduction:
In 2024 a global pilot study was performed on testing for the Contact Factors Prekallikrein (PK) and High Molecular Weight Kininogen (HK). This pilot study was a collaboration between the ECAT Foundation (The Netherlands), UKNEQAS for Blood Coagulation (United Kingdom) and RCPAQAP (Australia)
The pilot study was carried out on behalf of the EQATH group following a questionnaire to EQA providers about tests performed by small numbers of centres in each individual EQA programme. This study therefore investigated the feasibility of an external quality assessment survey for Contact Factors.
Materials and Methods:
Five different samples with different concentration for PK and HK were distributed. Samples with decreased levels for either Prekallikrein or High Molecular Weight Kininogen were prepared from mixing congenital deficient plasma with normal pooled plasma. The samples were buffered (Hepes) and lyophilised before distribution to the participants. Participants had the ability to report results for a screening test (APTT) and/or a functional quantitative test (APTT-based calibrated assay).
Results:
Thirty laboratories took part in this pilot survey, of which 19 laboratories submitted results. Nine laboratories reported results for a screening test (modified APTT test), while 15 laboratories reported results for quantitative testing for PK and/or HK.
With the screening tests a heterogeneity in the interpretation was found depending on the concentration for PK and/or HK. For the quantitative tests the between-laboratory variation varied between 20% and 84%. Also for the quantitative tests heterogeneity in the interpretation was found depending on the concentration for PK and/or HK.
Conclusion:
This pilot study has demonstrated the need for regular external quality control for contact factors. There is also a need for improvement of the inter-laboratory comparability of test results.