A practical guide to chimerism analysis: Review of the literature and testing practices worldwide

Background and Purpose: Currently there are no widely accepted guidelines for chimerism analysis test-ing in hematopoietic cell transplantation (HCT) patients. The objective of this review is to provide a prac-tical guide to address key aspects of performing and utilizing chimerism testing results. In developing this guide, we conducted a survey of testing practices among laboratories that are accredited for performing engraftment monitoring/chimerism analysis by either the American Society for Histocompatibility & Immunogenetics (ASHI) and/or the European Federation of Immunogenetics (EFI). We interpreted the survey results in the light of pertinent literature as well as the experience in the laboratories of the authors. Recent developments: In recent years there has been significant advances in high throughput molecular methods such as next generation sequencing (NGS) as well as growing access to these technologies in his-tocompatibility and immunogenetics laboratories. These methods have the potential to improve the per-formance of chimerism testing in terms of sensitivity, availability of informative genetic markers that distinguish donors from recipients as well as cost. Summary: The results of the survey revealed a great deal of heterogeneity in chimerism testing practices among participating laboratories. The most consistent response indicated monitoring of engraftment within the first 30 days. These responses are reflective of published literature. Additional clinical indica-tions included early detection of impending relapse as well as identification of cases of HLA-loss relapse. (c) 2021 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.