The diagnosis is suggested by Thrombocytopenia and anemia Fragmented red blood cells on the blood smear indicative of microangiopathic hemolysis (schistocytes: helmet cells, triangular RBCs, distorted-appearing RBCs) Evidence of hemolysis (falling hemoglobin level, polychromasia, elevated reticulocyte count, elevated serum LDH and bilirubin, reduced haptoglobin) Negative direct antiglobulin test Normal ADAMTS13 activity Diagnosis of cause Stool testing (Shiga toxin enzyme-linked immunosorbent assay or specific culture media for E coli O157: H7) is done in children with diarrhea and also adults who had a prodrome of bloody diarrhea; however, the organism and toxin may have cleared by the time of presentation.