How to further investigate aplastic anemia?

Comprehensive Diagnostic Approach to Aplastic Anemia

A thorough diagnostic evaluation for aplastic anemia requires bone marrow biopsy as the cornerstone of diagnosis, along with comprehensive peripheral blood analysis and specialized testing to distinguish it from other hypocellular bone marrow disorders. 1

Initial Diagnostic Workup

Peripheral Blood Assessment

• Count at least 100 cells on peripheral blood film 2
• Evaluate for:
  • Pancytopenia (decreased red cells, white cells, and platelets)
  • Absence of blasts
  • Minimal/absent dysplasia in granulocytes
  • Reticulocyte count (typically low)

Bone Marrow Evaluation

• Bone marrow biopsy is critical and necessary for diagnosis 2, 1

  • Assess for hypocellularity (<20% in severe cases)
  • Evaluate age-adjusted cellularity (essential for accurate diagnosis)
  • Obtain 1-2 cm core biopsy with 4-5 undistorted fields under 100x magnification
  • Perform reticulin stain to assess for fibrosis

• Bone marrow aspirate:

  • Perform 500 cell differential when possible 2
  • Examine for dysplasia of erythroid precursors, granulocytes, and megakaryocytes (should be minimal/absent)
  • Perform iron stain to rule out ring sideroblasts (>5 granules surrounding nuclear membrane excludes aplastic anemia) 2, 1

Distinguishing from Other Hypocellular Disorders

Key Differential Features

• Absence of abnormal localization of immature precursors (ALIP) 2
  • Presence of two or more clusters of immature precursors (minimum of three blasts/clusters) suggests MDS or AML
• Absence of significant dysplasia in any cell lineage 2
• Absence of increased blasts (<5% blasts) 2

Additional Essential Testing

• Standard cytogenetics/interphase FISH 2
  • Abnormal cytogenetics suggest MDS or leukemia rather than aplastic anemia
• Flow cytometry 2
  • To assess for abnormal cell populations
• PNH screening by sensitive flow cytometry 2
  • PNH clones are found in up to 50% of aplastic anemia patients

Diagnostic Accuracy Considerations

• Single bone marrow aspirate plus peripheral blood has a diagnostic accuracy of only ~54% 1
• Adding bone marrow biopsy increases diagnostic accuracy to ~95% 1
• Cases with diagnostic uncertainty should be reviewed by at least two experienced observers 2

Potential Treatment Considerations Based on Diagnosis

Once aplastic anemia is confirmed, treatment options include:

• Immunosuppressive therapy with antithymocyte globulin and cyclosporine 3
• Bone marrow transplantation (preferred for severe aplastic anemia with HLA-identical donor) 4
• Eltrombopag may be considered for refractory severe aplastic anemia 5

Common Pitfalls to Avoid

• Inadequate bone marrow sampling: Ensure sufficient biopsy size (1-2 cm) 2
• Misinterpreting focal granulocytic hyperplasia: Can be mistaken for early MDS 2
• Failure to perform age-adjusted cellularity assessment: Critical for accurate diagnosis 2
• Missing subtle dysplasia: Careful examination of all cell lineages is essential 2
• Relying solely on bone marrow aspirate: Biopsy is necessary for accurate diagnosis 2, 1

By following this comprehensive diagnostic approach, clinicians can accurately diagnose aplastic anemia and distinguish it from other hypocellular bone marrow disorders, enabling appropriate treatment selection to improve patient outcomes.