PB1092 - Results of samples spiked with chimeric monoclonal anti-PF4 antibody 1C12 in ECAT external quality assessment surveys for heparin-induced thrombocytopenia diagnosis.

Background: For the laboratory diagnosis of heparin-induced thrombocytopenia (HIT), the majority of laboratories are using an immunological assay to detect the presence of anti-PF4/heparin antibodies. Recently, chimeric monoclonal platelet factor 4 (PF4)-specific antibodies with a human IgG1 Fc fragment have been developed, and they mimic immunological features of human HIT antibodies [1, 2].

Aims: In this study the response of the 1C12 monoclonal antibody in a wide range of frequently used HIT immunological tests was investigated in the HIT external quality assessment surveys of the ECAT Foundation.

Methods: Citrated plasma was spiked with different concentrations of 1C12 (5, 10 and 22 µg/mL). Samples were lyophilised and distributed by regular postal service to the participants (n=465). Results, including details on the methods used, have ben submitted electronically to the ECAT Foundation.

Results: In semi-quantitative methods, a positive response was found by 79%, 95% and 93% of the participants for samples with 5, 10 and 22 µg/mL antibodies, respectively. In quantitative methods, a positive response was reported by > 99% of the participants for any antibody concentration used.
The table shows the average OD values or U/mL obtained for the different antibody concentrations used in the surveys.
The between-laboratory variation in test results varied between 10 and 25%, depending on the method used, and is comparable to the one previously observed in surveys using plasma samples from HIT positive patients.

Conclusion(s): On the basis of the results obtained in the ECAT surveys, it can be concluded that samples spiked with the monoclonal antibody 1C12 are suitable for the analytical performance assessment of immunological HIT assays.

References:
1. Kizlik-Masson, C., et al., J Thromb Haemost, 2017; 15: 2065-2075.
2. Vayne, C., et al., Thromb Haemost, 2021; 121: 322-331.