Thrombotic Microangiopathy Diagnosis and Management

Diagnostic Criteria

The presence of normocytic anemia, schistocytes on blood smear, and the patient's age are key factors in diagnosing thrombotic microangiopathy (TMA), specifically thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), or cancer-associated microangiopathic hemolytic anemia (CA-MAHA) 1, 2
Schistocytes on blood smear are pathognomonic for microangiopathic hemolytic anemia and represent intravascular red blood cell fragmentation 1, 2

ADAMTS-13 activity level should be measured, with severe deficiency (<10 IU/dL) confirming TTP, and normal to moderately reduced (>10 IU/dL) suggesting alternative TMA diagnosis like aHUS or secondary causes 2
Complete blood count with platelet count should be performed, as thrombocytopenia (<150,000/mm³) is expected in TTP/HUS 1, 2
Lactate dehydrogenase (LDH) should be measured, as it is markedly elevated in hemolysis 2
Haptoglobin should be measured, as it is decreased or undetectable in intravascular hemolysis 2
Direct Coombs test should be negative to confirm non-immune hemolytic anemia 2
Serum creatinine should be measured, as elevated levels (≥1.5 mg/dL in adults ≥13 years) indicate renal involvement consistent with HUS 1
Reticulocyte count should be elevated as an appropriate marrow response to hemolysis 3

If TTP is suspected, plasma exchange must be initiated immediately before ADAMTS-13 results return, as delay increases mortality 4
If atypical HUS is diagnosed, complement inhibitor therapy (eculizumab) should be initiated urgently 2, 4
Medication review is essential, as certain drugs can trigger TMA (calcineurin inhibitors, chemotherapy agents) 4