What labs can be ordered for a pediatric patient with pancytopenia (low platelet, low hemoglobin, and low neutrophil counts)?

Laboratory Evaluation for Pediatric Pancytopenia

For a pediatric patient with pancytopenia (low platelet, low hemoglobin, and low neutrophil counts), a comprehensive diagnostic workup should include a bone marrow examination along with specific blood tests to determine the underlying cause.

Initial Laboratory Evaluation

Complete Blood Count and Peripheral Smear

• Complete blood count with differential to confirm pancytopenia 1
• Peripheral blood smear examination to assess for abnormal cell morphology, presence of blasts, or other abnormalities 1

Bone Marrow Evaluation

• Bone marrow aspiration and trephine biopsy are essential for diagnosis of the underlying cause of pancytopenia 1, 2
• Bone marrow studies should include:
  • Morphological examination
  • Cytogenetics (minimum of 15 metaphases)
  • Flow cytometry to determine cell lineage characteristics
  • Molecular genetics testing as indicated 1

Infectious Disease Testing

• HIV testing 1
• Hepatitis C virus (HCV) testing 1
• Other infection markers based on clinical suspicion

Autoimmune Evaluation

• Antinuclear antibodies (ANA) 1
• Erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP) 1
• Complement levels (C3, C4) 1

Nutritional Deficiency Assessment

• Vitamin B12 and folate levels (megaloblastic anemia is a common cause of pancytopenia) 2
• Iron studies (ferritin, iron, TIBC)

Coagulation Studies

• Prothrombin time (PT)
• Activated partial thromboplastin time (PTT)
• Fibrinogen or thrombin time (optional) 1

Additional Specialized Tests

• Platelet function assays 1
• von Willebrand screening if bleeding history is present 1
• Immunoglobulin levels (IgG, IgA, IgM) to rule out common variable immune deficiency 1
• HLA typing if bone marrow transplantation might be considered 1

Diagnostic Approach Based on Severity

For Severe Pancytopenia

• Priority should be given to bone marrow examination to rule out aplastic anemia, which presents with significantly lower absolute neutrophil counts compared to other causes of pancytopenia 3, 4
• Urgent referral to a pediatric hematologist is recommended

For Moderate Pancytopenia

• Initial laboratory workup as outlined above
• Consider observation with serial CBCs if the patient is stable and has no concerning features

Important Considerations

• Bone marrow examination is crucial in pancytopenia as the distribution of hematopoietic tissue may be heterogeneous, with some areas showing normal cellularity ("hot pockets") while others show hypocellularity 4
• The absolute neutrophil count (ANC) can help distinguish between different causes of pancytopenia, with significantly lower values typically seen in aplastic anemia 3
• Children with atypical features should be referred to a pediatric hematologist experienced in the assessment of pancytopenia 1
• Avoid unnecessary delay in diagnosis, particularly for aplastic anemia, which is a hematological emergency requiring prompt intervention 3

By following this systematic approach to laboratory evaluation, clinicians can efficiently identify the underlying cause of pancytopenia in pediatric patients and initiate appropriate management strategies.