What is the initial workup for a patient suspected of having aplastic anemia?

Aplastic Anemia Workup

The initial workup for suspected aplastic anemia requires bone marrow examination with aspirate and core biopsy as the cornerstone diagnostic test, combined with complete blood count, peripheral blood smear review, flow cytometry for PNH screening, and comprehensive ancillary testing to exclude other causes of pancytopenia. 1, 2

Essential Clinical Information to Obtain

• Document patient age, sex, ethnicity, and complete medical history including any prior hematologic disorders, known predisposing conditions, or inherited syndromes 3
• Obtain detailed exposure history to cytotoxic therapy, immunotherapy, radiotherapy, or potentially toxic substances (chemicals, medications) as therapy-related cases account for 5-20% of presentations 3
• Record recent confounding factors such as growth factor therapy, recent transfusions, or medications that might obscure diagnostic features 4, 3
• Document family history of hematologic disorders or malignancies 4, 3
• Perform physical examination specifically documenting organomegaly (liver, spleen), lymphadenopathy, cutaneous lesions, and hemorrhagic manifestations 3

Mandatory Laboratory Studies

Complete Blood Count and Peripheral Blood Evaluation

• Obtain CBC with differential showing pancytopenia (anemia, neutropenia, thrombocytopenia) 1, 2
• Review peripheral blood smear to assess cell morphology and exclude other causes 4, 3

Bone Marrow Examination (Critical)

• Obtain fresh bone marrow aspirate for morphologic evaluation with aspirate smears—this is mandatory for all suspected cases 4, 3
• Perform bone marrow trephine core biopsy to demonstrate hypocellularity with fatty replacement 4, 3
• Prepare touch imprint preparations if aspirate is inadequate or "dry tap" occurs 4, 3
• Submit additional core biopsy unfixed in tissue culture medium for flow cytometry and genetic studies if aspirate is unobtainable 4, 3

Flow Cytometry for PNH Screening

• Perform multiparameter flow cytometry on bone marrow or peripheral blood to detect GPI-anchor protein deficiency (CD55, CD59 deficiency) as PNH screening is essential at diagnosis 5, 6
• This test identifies aplastic anemia-PNH syndrome, which occurs in a subset of patients and requires different management 5

Cytogenetic and Molecular Testing

• Perform conventional karyotyping on bone marrow to exclude myelodysplastic syndrome (MDS) and identify chromosomal abnormalities 3, 5
• Conduct molecular genetic testing to rule out inherited bone marrow failure syndromes, particularly telomere repair gene mutations 2

Additional Laboratory Tests

• Obtain comprehensive metabolic panel, lactate dehydrogenase, uric acid, and phosphate levels 3
• Perform coagulation panel (PT, PTT, fibrinogen) to assess bleeding risk 7

Critical Differential Diagnoses to Exclude

Hypoplastic Myelodysplastic Syndrome

• Differentiate from aplastic anemia by identifying dysplastic cell morphology and chromosomal abnormalities on bone marrow examination 5
• Hypoplastic MDS exhibits abnormal cell morphology despite hypocellular marrow, whereas aplastic anemia shows normal morphology of residual cells 5

Paroxysmal Nocturnal Hemoglobinuria

• Flow cytometry for GPI-anchor proteins is mandatory as some patients initially diagnosed with aplastic anemia later develop overt PNH 5, 6

Other Causes of Pancytopenia

• Rule out megaloblastic anemia (vitamin B12, folate levels), hypersplenism, and other bone marrow infiltrative processes through bone marrow examination 1, 2

Common Pitfalls to Avoid

• Do not rely solely on peripheral blood findings—bone marrow examination is essential as pancytopenia alone is insufficient for diagnosis 1, 2
• Do not skip PNH screening with flow cytometry—this is frequently underutilized (only 55.5% of patients tested in real-world practice) but critical for appropriate management 6
• Do not delay diagnostic workup—median time from diagnosis to treatment in real-world practice is 22 days, with older patients experiencing longer delays 6
• Ensure adequate bone marrow specimen collection; if initial aspirate yields "dry tap," obtain touch preparations and additional core biopsy for disaggregation 4, 3

Severity Classification After Diagnosis

• Classify as severe AA if absolute neutrophil count <500/μL, platelet count <20,000/μL, and reticulocyte count <20,000/μL with hypocellular bone marrow 1
• Identify heavily transfusion-dependent patients (HT-AA) versus less transfusion-dependent patients (LT-AA) as this determines treatment approach 6