RCI Genotyping for Therapeutic Monoclonal Antibody Patients

It is standard procedure in RCI to obtain a full cell type on all patients receiving, or due to commence, therapeutic monoclonal antibody (TMAb) therapy. This is performed serologically where possible, but molecular typing may be employed if the patient has received a recent transfusion or is DAT positive. This testing is performed by RCI both when directly requested by the referring Hospital and on all new referrals even if not directly requested by the Hospital laboratory. 

Due to a national shortage of DNA extraction kits, RCI will be modifying their approach for the next few months to conserve stocks. Full cell types will still be completed by serological phenotyping where possible. If phenotyping cannot be performed, molecular testing will still be performed if the patient is receiving anti-CD47 TMAbs, if RCI do not have a resolved Rh (C, c, E, e) or K type, if the patient is K+, or if the patient has additional red cell alloantibodies.

In the interim, genotyping will be omitted for anti-CD38 patients who have a resolved Rh type and are known to be K-. Once DNA extraction kit stock levels have returned to normal, likely in January 2023, these patients will have a genotype performed on the next referred sample. 

This interim procedural change has been assessed as low risk due to the robust antibody identification methodologies utilised by RCI in these cases as well as the low reported rates of alloimmunisation in TMAb patients (see Bullock, et al, 2021; Tauscher, et al, 2021). 

Any questions can be referred to your RCI laboratory. 

References

Bullock, T; Foster, A; Clinkard, B (2021) Alloimmunisation rate of patients on Daratumumab: A retrospective cohort study of patients in England Transfusion Medicine 31: 474-480 

Tauscher, C; Moldenhauer, S; Bryant, S; DiGuardo, M and Jacob, E (2021) Antibody incidence and red blood cell transfusions in patients on Daratumumab. Transfusion 61(12):3468-3472  

Mark Dwight, Senior Biomedical Scientist, RCI Filton