Which laboratory finding best distinguishes intravascular from extravascular hemolysis?
- A Hemoglobinuria with markedly reduced serum haptoglobin ✓
- B Elevated serum LDH
- C Reticulocytosis and indirect hyperbilirubinemia
- D Spherocytes on peripheral smear
Correct answer: A. Hemoglobinuria with markedly reduced serum haptoglobin
Explanation
Free hemoglobin released directly into plasma during intravascular hemolysis saturates and depletes haptoglobin, and excess hemoglobin is filtered by the kidney producing hemoglobinuria — features specific to intravascular hemolysis. Elevated LDH, reticulocytosis, and indirect hyperbilirubinemia occur in both intravascular and extravascular hemolysis. Spherocytes are characteristically seen in extravascular hemolytic conditions such as hereditary spherocytosis and AIHA.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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