New supplementary examinations from 1 November 2021

Dear Contracting Authorities,

In recent years, there has been an increasing trend in the number of hematopoietic cell transplants performed from haploidentical related donors. Such a donor matches the patient in only one HLA haplotype (minimum 5/10 match). In case of disease relapse, the patient may lose the mismatched specific HLA haplotype due to genetic rearrangement. This condition is referred to as HLA loss relapse. Distinguishing HLA loss relapse from classic relapse is important to determine the subsequent treatment strategy. In the case of HLA loss relapse, the administration of DLI is ineffective; on the other hand, due to the loss of heterozygosity, leukemia cells are provided with a selective advantage that allows them to escape the immunological pressure of alloreactive donor T cells. These then invade the healthy tissues of the patient and may lead to a graft-versus-host reaction.

For this reason, we have newly introduced the testing of novel markers localized in the HLA region based on quantitative real-time PCR using the commercial HLA-KMR® assays kit (GenDx). This will allow us to distinguish classic relapse from HLA loss relapse in case of autologous hematopoiesis. It is most often encountered after haploidentical transplants.

Based on the request of the physicians of the Institute of Human Transplantation, the informativeness test for post-transplant monitoring will be supplemented with information on whether a suitable HLA marker for determining the type of relapse is available based on HLA genotyping. In case of an increase in autologous hematopoiesis (detection of mixed chimerism in non HLA markers), patients after haploidentical transplantation will also be automatically quantified in HLA marker if available.

The additional testing will be introduced into the accredited scheme from 1.11.2021.

Thank you.

Mgr. Hana Čechová