Rapid genomic analysis for early identification of complement abnormalities in adults with transplant-associated thrombotic microangiopathy

Background: Transplant-associated thrombotic microangiopathy is a severe and often fatal complication of allogeneic hematopoietic cell transplantation; early identification of the involved mechanisms may enable timely therapy. Study design: Adult recipients of allogeneic hematopoietic cell transplantation (n = 195) were studied in the early post-transplant period. The recent harmonizing criteria from the world's leading blood and marrow transplant societies, such as ≥4 of 7 specific clinical/laboratory features for thrombotic microangiopathy diagnosis were applied. Plasma levels of sC5b-9, a marker of complement activation, was measured by an enzyme-linked immunosorbent assay and complement-related genes in blood cells were evaluated by both rapid genomic analyses using nanopore sequencing and conventional methods (targeted next generation sequencing and multiplex ligation-dependent probe amplification assay). Results: Ten patients who met ≥4 criteria (confirmed transplant-associated thrombotic microangiopathy) had high 1-year non-relapse mortality (60%) and high complement activation. In this group, plasma levels of sC5b-9 were higher than in patients without confirmed disease (p-value = 0.04) and normal controls (p-value <0.001). At the same time (after full chimerism), they showed seven rare variants of complement related genes (minor allele frequency <0.03). Rapid genomic analysis identified these alterations with complete concordance to conventional methods. Conclusions: These results support the utility of applying harmonized criteria for early diagnosis of transplant-associated thrombotic microangiopathy and performing rapid genomic analysis with nanopore sequencing for the identification of variants in complement-related genes within 72h. Future studies on larger cohorts could explore the integration of rapid genomic analysis in this patient population and potentially for screening donors whose cells may carry genetic alterations for real-time clinical decision making.