What is the role of a CBC count in the workup of hemolytic disease of the newborn (HDN)?

Updated: Dec 28, 2017
  • Author: Sameer Wagle, MBBS, MD; Chief Editor: Muhammad Aslam, MD  more...
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Answer

The severity of hematologic abnormalities is directly proportional to the severity of hemolysis and the extent of hematopoiesis. The following abnormalities are observed on complete blood cell (CBC) count findings:

  • Anemia: Measurements are more accurate using central venous or arterial samples rather than capillary blood.

  • Increased nucleated red blood cells (RBCs), reticulocytosis, polychromasia, anisocytosis, spherocytes, and cell fragmentation

    • The reticulocyte count can be as high as 40% in patients without intrauterine intervention.

    • The nucleated RBC count is elevated and falsely elevates the leukocyte count, reflecting a state of erythropoiesis.

    • Spherocytes (<40%) are more commonly observed in cases of ABO incompatibility. Glucose does not correct the autohemolysis in ABO incompatibility unlike hereditary spherocytosis.

    • In severe hemolytic disease, schistocytes and burr cells may be observed, reflecting ongoing disseminated intravascular coagulation (DIC).

    • In neonates with sepsis, risk factors for DIC include asphyxia, bleeding, and gram-negative bacterial infection. [34]

    • A low reticulocyte count is observed in fetuses provided with intravascular transfusion in utero and with Kell alloimmunization.

    • Abnormally elevated mean cell hemoglobin concentration (MCHC) and red cell distribution width (RDW) values should prompt a diagnosis of hereditary spherocytosis. [35]

  • Neutropenia: This condition seems to be secondary to stimulation of erythropoiesis in favor of myelopoiesis. However, neutrophilia can be observed after intrauterine transfusion because of an increase in circulating cytokines (granulocyte-macrophage colony-stimulating factor).

  • Thrombocytopenia: This condition is common, especially after intrauterine or exchange transfusions because of platelet-poor blood product and suppression of platelet production in favor of erythropoiesis.


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