What is the appropriate evaluation, diagnostic work‑up, and management for a patient suspected of aplastic anemia?

Evaluation, Diagnosis and Management of Aplastic Anemia

Initial Clinical Assessment

For any patient with suspected aplastic anemia, immediately obtain a complete blood count with differential, peripheral blood smear, reticulocyte count, and proceed urgently to bone marrow biopsy and aspirate—delays in diagnosis directly worsen outcomes regardless of eventual treatment choice. 1, 2, 3

Essential History Elements

• Document exposure history: cytotoxic therapy, immunotherapy, radiotherapy, or toxic substances (accounts for 5-20% of cases) 2
• Identify predisposing conditions: prior hematologic disorders, inherited syndromes, autoimmune disease history (personal and family) 1, 2
• Recent confounding factors: growth factor therapy, recent transfusions, or medications that might obscure diagnostic features 2
• Family history: hematologic disorders or malignancies to identify inherited bone marrow failure syndromes 2

Physical Examination Priorities

• Assess for spleen size: splenomegaly suggests alternative diagnoses (myeloproliferative disorders, lymphoma) rather than aplastic anemia 1
• Document organomegaly, lymphadenopathy, cutaneous lesions, and hemorrhagic manifestations 2

Mandatory Diagnostic Workup

Peripheral Blood Evaluation

• Count at least 100 cells on peripheral smear to enumerate granulocyte dysplasia and assess for blasts 4
• Reticulocyte count is essential for severity grading 1, 2

Bone Marrow Examination (Critical and Non-Negotiable)

A bone marrow biopsy is absolutely essential—aspirate alone is insufficient due to typical paucicellularity in aplastic anemia. 4

• Obtain fresh bone marrow aspirate for morphologic evaluation with aspirate smears 2
• Perform 500-cell differential if possible, examining for dysplasia of erythroid precursors, granulocytes, and megakaryocytes 4
• Iron stain for ring sideroblast assessment (>5 granules surrounding nuclear membrane excludes aplastic anemia diagnosis) 4
• Obtain 1-2 cm trephine core biopsy to assess cellularity (must visualize 4-5 undistorted fields under 100x magnification) 4
• If "dry tap" occurs: prepare touch imprint preparations and obtain additional core biopsy unfixed in tissue culture medium for flow cytometry and genetic studies 2
• Reticulin stain on biopsy 4

Cellularity Assessment

• Estimate bone marrow cellularity using age-adjusted criteria: normal cellularity = 100 - age (±10%) 4
• Hypocellularity must be below age-adjusted normal range to diagnose aplastic anemia 4

Ancillary Studies (Mandatory)

• Standard cytogenetics/karyotype: cannot be replaced by FISH or molecular testing 4
• Flow cytometry: to exclude abnormal phenotypes and distinguish from hypoplastic MDS 4, 1
• PNH screening: by sensitive flow cytometry or molecular technique (GPI-anchored proteins CD16, CD55, CD59) 4, 5
• Immunohistochemistry: assess for ALIP (abnormal localization of immature precursors) using CD34, CD117, myeloperoxidase stains 4

Additional Laboratory Tests

• Viral studies: HIV, HBV, HCV, CMV, EBV, parvovirus B19 1, 6
• Comprehensive metabolic panel, LDH, uric acid, phosphate 2
• Coagulation panel (PT, PTT, fibrinogen) to assess bleeding risk 2
• Vitamin B12, folate, copper levels to exclude nutritional causes 1

Critical Differential Diagnosis

Distinguishing Aplastic Anemia from Hypoplastic MDS/AML

The presence of ≥20% blasts on aspirate definitively excludes aplastic anemia and establishes AML diagnosis. 4

Key features that exclude aplastic anemia and indicate MDS/AML:

• Moderate to severe erythroid dysplasia: binucleated/trinucleated forms, numerous Howell-Jolly bodies, nuclear budding or bridging 4
• Abnormal sideroblasts: >5 granules surrounding nuclear membrane or occupying ≥1/3 of circumference 4
• ALIP presence: ≥2 clusters of immature precursors (minimum 3 blasts/cluster) in bone marrow biopsy 4
• Cytogenetic abnormalities: strongly suggest MDS over aplastic anemia 4

PNH-Aplastic Anemia Syndrome

• Some aplastic anemia patients have cells partially lacking GPI anchor proteins at diagnosis 5
• Monitor for evolution to overt PNH during disease course 5

Severity Grading

Severity classification determines treatment urgency and approach:

• Severe aplastic anemia: bone marrow cellularity <25% (or 25-50% with <30% residual hematopoietic cells) PLUS at least 2 of: ANC <500/μL, platelets <20,000/μL, reticulocytes <20,000/μL 1
• Very severe: meets severe criteria with ANC <200/μL 1
• Moderate/non-severe: pancytopenia not meeting severe criteria 1

Treatment Algorithm

First-Line Treatment Selection

For patients <40-50 years with severe aplastic anemia and HLA-identical sibling donor: proceed immediately to allogeneic hematopoietic stem cell transplantation—this is the only curative option. 1, 6, 7

For patients without matched sibling donor or age >40 years: initiate immunosuppressive therapy with horse antithymocyte globulin (ATG) plus cyclosporine A plus eltrombopag. 1, 6, 7

Immunosuppressive Therapy Protocol

• Horse ATG (preferred over rabbit ATG based on superior response rates) 6, 7
• Cyclosporine A: administer for minimum 6 months 6
• Eltrombopag: added to standard horse ATG/cyclosporine regimen (improves response rates to ~82%) 1, 5

Supportive Care (All Patients)

• Transfusion support: use irradiated and filtered blood products 1
• Platelet transfusions: maintain platelets to prevent bleeding complications 1
• Growth factor support (G-CSF): may be considered for severe neutropenia with infections, though continuous use lacks evidence 4
• Infection prophylaxis and treatment: critical during neutropenic periods 1

Refractory/Relapsed Disease

For patients failing initial immunosuppressive therapy: consider alternative donor transplantation (matched unrelated donor or cord blood). 6, 3

• Second-line IST options: repeat ATG course, alternative immunosuppressive agents 3
• Best supportive care: reasonable for patients unsuited to aggressive approaches 3

Monitoring Strategy

During Initial Treatment

• Weekly CBC during initial treatment phase 1
• Monitor for response: improvement in blood counts, reduction in transfusion requirements 1
• For patients on eltrombopag: regular liver function test monitoring with dose adjustment based on platelet response 1

Long-Term Surveillance

• Monitor for incomplete response, relapse, and evolution to MDS/acute leukemia: these remain significant long-term complications even after successful IST 3
• Ongoing assessment for therapy-related side effects 3

Critical Pitfalls to Avoid

Never delay treatment initiation while awaiting complete diagnostic workup—time from diagnosis to treatment directly impacts outcome. 3

Failure to distinguish aplastic anemia from hypocellular MDS or hypocellular AML leads to inappropriate treatment: always obtain adequate bone marrow biopsy with full ancillary studies before finalizing diagnosis. 4, 1

Do not rely on aspirate alone: the paucicellularity typical of aplastic anemia makes aspirate specimens inadequate for definitive diagnosis. 4

Avoid using rabbit ATG when horse ATG is available: horse ATG demonstrates superior efficacy in immunosuppressive therapy regimens. 7