Sickle cell disease patients in two London trusts: Genotyping including RH variants

Background: All SCD patients need extended RBC antigen typing (by serology or genotyping) for provision of extended RH, K matched blood and to guide RBC selection in those with complex transfusion requirements. Genotyping can also identify RH variants which can cause sensitisation even when extended RH phenotypically matched blood is provided and alloantibodies associated with RH variants can cause HTRs.

Objectives: To review the use of RBC genotyping in SCD patients at two London trusts (ICHNT, LNWH) with a focus on RH variants.

Methods: Retrospective review with data collected from clinical notes, local and national pathology reporting systems.

Results: A 311/482 (64%) ICHNT patients and 181/346 (52%) LNWH patients had extended genotyping. Of genotyped patients, 68 (22%) ICHNT and 31 (17%) LNWH patients had RH variants. Eight ICHNT patients had RH variants and corresponding antibodies associated with RH variants; 4/8 received multiple transfusions with antigen positive RBCs but had no evidence of haemolysis. One LNWH patient had a RH variant with corresponding alloantibody but could not be investigated further for possible HTR.

Conclusions: Most patients (59%) had genotyping and a significant number had RH variants (99, 20%). A small proportion (9, 9%) had antibodies associated with RH variants, but with no evidence of clinically significant HTRs despite transfusions in four of them with antigen positive RBCs. All SCD patients should have RBC genotyping including RH variants (preferentially over extended phenotyping) to guide better selection of RBC units. However, where antigen negative blood cannot be provided, the risk of alloimmunisation is not inevitable and subsequent HTRs from antibodies associated with RH variants might not always occur.