Automated measurement of schistocytes after bone marrow transplantation

Bone marrow transplantation-related thrombotic microangiopathy (BMT-TMA) is a severe complication partly suspected on the evidence of a microangiopathic haemolysis. Microscopic schistocyte observation confirms the mechanical origin of the haemolysis, but remains a tedious procedure that lacks standardization. Direct measurement of abnormal red blood cell (RBC) fragments is now available on some automated haematology systems. We compared in 131 patients (69 BMT with five BMT-TMA, 38 thrombotic thrombocytopenic syndromes, 11 macroangiopathies, 13 dyserythropoiesis) percentages of microscopic schistocytes and automated RBC fragments (Bayer ADVIA 120) to evaluate the clinical relevance of the automated measurements for BMT-TMA detection. The analyser correlated well with the microscope (intraclass correlation coefficient: 0.82) and quantified RBC fragments with a moderate overestimation (+0.4%) as compared to microscopic counts. BMT patients had higher RBC fragments when they had TMA (1.1 vs 0.4% without TMA). Automated counting was useful to flag BMT-related TMA, particularly when RBC fragments were above 1%. As RBC fragments were frequently detected in BMT patients even without TMA, a threshold of less 1% that ruled out TMA was determined with a 98% negative predictive value. The new RBC fragment automated parameter proved its clinical value to assess BMT-TMA, which might be useful for day-to-day monitoring of the post BMT period.