Microscopic schistocyte determination according to International Council for Standardization in Hematology recommendations in various diseases

Summary Introduction Recently, a consensus report for microscopic schistocyte determination was prepared by International Council for Standardization in Hematology (ICSH). ICSH focused on diagnosis of thrombocytopenic purpura (TTP)/hemolytic uremic syndrome (HUS). We aimed to reanalyze schistocytes according to ICSH recommendations, to study diseases other than TTP/HUS related to the schistocytes, and to compare the percentage of schistocytes among the various diseases. Methods We retrieved all reported cases of peripheral blood (PB) smear in a single institution during 6 years. Schistocytes on 282 PB smears showing previous peripheral schistocytes and hemoglobin ≤10 g/dL were recounted according to ICSH recommendations. Results The schistocytes were frequently observed in patients with microangiopathic hemolytic anemia (MAHA), metastatic carcinoma, sepsis, chronic renal failure, preterm infant, and infection. Only two among 34 patients categorized as MAHA were diagnosed as TTP/HUS. Schistocytes were observed with other morphological changes in 169 of 170 cases with schistocyte ≤1% and in 102 of 112 with schistocyte >1%. The median schistocyte percentages of patients with hematologic malignancy, megaloblastic anemia, acute renal failure, and preterm infant were 1.20%, 1.30%, 1.35%, and 1.70%, respectively. Conclusion Schistocytes were observed above 1% in many diseases other than TTP /HUS. Therefore, it is important to understand that schistocytes could be seen in various diseases, and in these cases, schistocytes were usually detected together with other red blood cell morphologic changes. These data support ICSH recommendation that a schistocyte count should be considered clinically meaningful if schistocytes represent the main morphological abnormality in the PB smear.