Evaluation of schistocyte monitoring after haematopoietic stem cell transplantation.

INTRODUCTION

Observation of schistocytes on the peripheral blood following haematopoietic stem cell transplantation (SCT) is a common finding. As their presence is not specific to the onset of SCT-related thrombotic microangiopathy, we evaluated the interest of schistocyte measurement twice a week during the entire follow-up of 195 patients undergoing SCT, particularly focussing on the 125 allogeneic SCT.

METHODS

Schistocytes were strickly defined as triangular-, crescent- or helmet-shaped red blood cells according to consensus standards and were checked blindly under the microscope and with computer image analysis.

RESULTS

Mean schistocyte percentage was 0.7% (±0.5%, reference value ≤0.5). High schistocyte percentage was observed after allografts (0.79%) when compared to autologous SCT (0.47, P < 0.001). All but one patients undergoing allogenic SCT had schistocytes ≥0.6%. Conversely, significant schistocytosis was observed in 20% of the autologous SCT. Initial diagnosis [chronic myelocytic leukaemia, acute lymphoblastic leukaemia (ALL)], high-risk status, unrelated transplant and conditioning regimen including total body irradiation influenced higher schistocyte percentage (≈0.9%). Significant rise in the schistocyte percentage was observed during acute/chronic graft-versus-host disease, veno-occlusive disease (VOD), cholestatic hepatitis, haemorrhagic cystitis (HC) and pulmonary complications. Multivariate analysis showed a significant association between thrombotic microangiopathy (TM), renal impairment and delayed thrombopaenia after day 50, and schistocyte >1.2%. SCT-TM grade ≥2 occurred in nine patients. A marked rise in schistocyte >4.5% was observed, which was not reached during the other SCT-related complications. Children with ALL, undergoing unrelated allogeneic SCT, with early acute graft-versus-host disease refractory to steroids were prone to present SCT-TM, associated with VOD, interstitial pneumopathy and HC, resulting in a high mortality rate (six of seven patients). Our data confirmed that schistocytosis was common after SCT. Mild percentages were likely concomitant with extensive endothelial damage but higher percentage should have prompted to a close monitoring with SCT-TM investigation.

CONCLUSION

In our experience, systematic schistocyte count after HSCT proved to be useful: the occurrence of an increased percentage was a surrogate marker for complications even if unspecific for TM.