What are the typical complete blood count (CBC) results for pediatric patients with leukemia?

Complete Blood Count Results in Pediatric Leukemia

Pediatric leukemia typically presents with abnormal complete blood count results including leukocytosis, anemia, and thrombocytopenia, though the specific pattern varies by leukemia type and disease stage. 1

Key CBC Findings in Pediatric Leukemia

White Blood Cell (WBC) Parameters

• Total WBC count:

  • Often elevated (leukocytosis), particularly in acute lymphoblastic leukemia (ALL)
  • Median WBC in pediatric chronic myeloid leukemia (CML) is approximately 240,000/μL 1
  • In ALL, higher WBC counts (>100,000/μL) are associated with poorer prognosis 2
  • Some patients may present with normal or even decreased WBC counts

• Differential count abnormalities:

  • Presence of blast cells in peripheral blood
  • Abnormal distribution of neutrophils, lymphocytes, and monocytes
  • Left shift (increased immature neutrophils)
  • Increased basophils and/or eosinophils (particularly in CML) 1

Red Blood Cell (RBC) Parameters

• Hemoglobin/Hematocrit:

  • Typically decreased (anemia)
  • Mild anemia in CML chronic phase 1
  • More severe anemia often seen in acute leukemias

• RBC morphology:

  • May show abnormalities in shape and size
  • Nucleated RBCs may be present in severe disease

Platelet Parameters

• Platelet count:
  • Usually decreased (thrombocytopenia)
  • In CML chronic phase, platelet counts may be normal or elevated 1
  • In ALL, approximately 17.8% of children may have normal platelet counts at diagnosis 3
  • Thrombocytopenia is more common in acute non-lymphoblastic leukemia (ANLL), with only 3.7% having normal platelet counts 3

Specific CBC Patterns by Leukemia Type

Chronic Myeloid Leukemia (CML) - Chronic Phase

• High WBC count (median 240,000/μL)
• Mild anemia
• Normal or elevated platelet counts
• Increased basophils and eosinophils
• Pathological shift to the left (increased immature granulocytes) 1

Acute Lymphoblastic Leukemia (ALL)

• Variable WBC count (can be normal, decreased, or markedly elevated)
• Moderate to severe anemia
• Thrombocytopenia in approximately 82% of cases 3
• Presence of lymphoblasts in peripheral blood

Acute Myeloid Leukemia (AML)

• Variable WBC count
• Moderate to severe anemia
• Thrombocytopenia in approximately 96% of cases 3
• Presence of myeloblasts in peripheral blood

Clinical Correlations with CBC Findings

• Higher WBC counts in ALL correlate with:

  • Poorer event-free survival
  • Higher risk of relapse
  • Poorer overall prognosis 2

• Patients without thrombocytopenia in ALL tend to have:

  • Less marked leukocytosis
  • Less severe anemia
  • Lower percentage of bone marrow blasts
  • Better continuous complete remission rates 3

Diagnostic Approach

When interpreting CBC results in suspected pediatric leukemia:

1. Complete CBC with differential should include:

   • Full WBC count and differential
   • Hemoglobin and hematocrit
   • Platelet count
   • Manual differential to identify blasts and abnormal cells 1, 4

2. Bone marrow examination is required for definitive diagnosis:

   • Morphology
   • Blast percentage
   • Cytogenetics
   • Flow cytometry 1

3. Additional testing based on CBC abnormalities:

   • Molecular genetics for fusion transcripts
   • Immunophenotyping
   • Cytogenetic analysis 1

Important Caveats

• A normal CBC does not rule out leukemia, particularly in early stages
• Some children with ALL may present with normal platelet counts (17.8%) 3
• CBC results must be interpreted in the clinical context
• Serial CBCs may be more informative than a single measurement
• Pre-analytical errors can occur if samples are not processed within 24 hours 4

Remember that while CBC abnormalities often prompt the investigation for leukemia, the definitive diagnosis requires bone marrow examination with morphologic, immunophenotypic, and genetic studies.