What is the appropriate initial evaluation and work‑up for a patient presenting with pancytopenia?

Evaluation of Pancytopenia

Initial Laboratory Assessment

Begin with a complete blood count with differential and peripheral blood smear examination to confirm true pancytopenia and identify critical morphological abnormalities such as blasts, schistocytes, or dysplastic features. 1

• Obtain reticulocyte count immediately to differentiate between bone marrow production failure (low reticulocyte count) versus peripheral destruction or sequestration (elevated reticulocyte count). 1
• Perform peripheral smear review by a pathologist or hematologist to exclude pseudothrombocytopenia from platelet clumping and to identify blasts, which mandate urgent hematology consultation. 2, 1
• Measure lactate dehydrogenase (LDH), haptoglobin, indirect bilirubin, and direct antiglobulin test (Coombs) to assess for hemolysis or ineffective hematopoiesis. 1, 2

Essential Infectious and Nutritional Workup

• Test all adult patients for HIV and hepatitis C virus (HCV) regardless of risk factors, as these infections are common reversible causes of pancytopenia. 1, 3
• Obtain vitamin B12, folate, and complete iron studies (serum iron, TIBC, ferritin) before initiating any treatment, as megaloblastic anemia is a frequent and rapidly correctable cause. 1, 4
• Consider parvovirus B19 PCR in cases with hypoplastic bone marrow pattern or pure red cell aplasia features. 1
• Perform Helicobacter pylori testing in adults, as eradication may improve cytopenias in some cases. 1

Autoimmune and Systemic Disease Screening

• Check antinuclear antibodies (ANA), anti-dsDNA, and antiphospholipid antibodies when systemic symptoms (fever, rash, arthralgia) or physical findings (serositis, lymphadenopathy) suggest autoimmune disease. 2, 1
• Measure thyroid-stimulating hormone (TSH) and antithyroid antibodies as thyroid dysfunction can contribute to cytopenias. 2
• Obtain quantitative immunoglobulin levels particularly in children or when recurrent infections are present. 2

Indications for Bone Marrow Examination

Perform bone marrow aspiration AND biopsy simultaneously with cytogenetic analysis in any of the following scenarios: 1, 3, 5, 4

• Age greater than 60 years (higher risk of myelodysplastic syndromes and hematologic malignancies) 1
• Presence of blasts on peripheral smear (requires immediate evaluation for acute leukemia) 1, 3
• Reticulocyte count less than 1.5% without obvious nutritional deficiency (suggests bone marrow production failure) 1
• Systemic symptoms including fever, night sweats, weight loss, or abnormal physical findings such as hepatosplenomegaly or lymphadenopathy 1, 3
• Unclear diagnosis after initial laboratory workup 1
• Any patient on immunotherapy with persistent or progressive cytopenias (to exclude marrow infiltration, secondary MDS, or aplastic anemia) 1, 3

Critical Technical Points for Bone Marrow Examination

• Both aspiration and biopsy must be performed together, as aspiration may be inadequate ("dry tap") in cases of fibrosis or packed marrow, while biopsy provides architectural assessment. 5, 4
• Cytogenetic analysis with minimum 15 metaphases is mandatory to identify chromosomal abnormalities essential for diagnosing MDS and determining prognosis. 3, 6
• Flow cytometry should be performed to define blast phenotype and exclude lymphoproliferative disorders. 3
• Special stains including Perl's iron stain, myeloperoxidase (MPO), PAS, and reticulin should be available and used as indicated. 5

Drug and Exposure History

• Obtain detailed medication history including over-the-counter drugs, herbal supplements, alcohol use, and recent chemotherapy or immunotherapy exposure. 2, 1
• Specifically inquire about methotrexate (even low-dose weekly therapy), sulfonamides, purine analogs, and immune checkpoint inhibitors, as these commonly cause pancytopenia. 1
• Document radiation exposure and occupational chemical exposures (benzene, pesticides). 1

Special Populations and Contexts

Immunotherapy-Treated Patients

• Monitor CBC at treatment initiation, during therapy, and periodically in long-term survivors to detect immune-related adverse events. 1
• Maintain low threshold for bone marrow examination to rule out marrow infiltration, secondary MDS, or aplastic anemia. 1, 3
• Note that 40% of immune-related autoimmune hemolytic anemia cases are Coombs-negative, requiring alternative diagnostic approaches including reticulocyte count and LDH assessment. 1
• Discontinue immunotherapy immediately while investigating significant hematological toxicity and obtain urgent hematology consultation. 1

Patients with Lymphadenopathy

• Perform excisional (not fine-needle aspiration) lymph node biopsy with histopathology, immunohistochemistry, flow cytometry, and microbiologic cultures when lymphadenopathy accompanies pancytopenia. 1
• Consider Rosai-Dorfman-Destombes disease, lymphoma, and mycobacterial infections (particularly MAC in HIV patients) in the differential diagnosis. 1

Pediatric Considerations

• Evaluate for inherited bone marrow failure syndromes including Fanconi anemia, dyskeratosis congenita, and SAMD9/SAMD9L-associated syndromes in children presenting with pancytopenia. 1
• Screen for hemophagocytic lymphohistiocytosis (HLH) when fever, hepatosplenomegaly, hypertriglyceridemia, hypofibrinogenemia, and elevated ferritin accompany pancytopenia. 1

Additional Testing in Selected Cases

• Copper and ceruloplasmin levels when history includes gastrointestinal surgery, vitamin B12 deficiency, or vacuolation of myeloid/erythroid precursors on bone marrow. 1
• ADAMTS13 activity level and inhibitor titer when thrombotic thrombocytopenic purpura (TTP) is suspected (schistocytes, hemolysis, renal insufficiency). 2
• Complement testing (C3, C4, CH50) for suspected atypical hemolytic uremic syndrome or complement-mediated hemolysis. 2
• HLA typing should be obtained early if allogeneic stem cell transplantation may become indicated (severe aplastic anemia, high-risk MDS). 3

Common Pitfalls to Avoid

• Do not rely on bone marrow aspiration alone—simultaneous biopsy is essential as aspiration frequently yields inadequate samples in fibrotic or hypocellular marrows. 5, 4
• Do not delay hematology consultation when blasts are present on peripheral smear or when bone marrow examination is indicated. 1, 3
• Do not assume normal reticulocyte count excludes hemolysis—calculate corrected reticulocyte count and reticulocyte production index to account for degree of anemia. 1
• Do not overlook medication-induced pancytopenia—methotrexate toxicity can occur 4-6 weeks after dose increases, particularly with renal impairment or concomitant sulfonamide use. 1
• Do not use fine-needle aspiration for lymph node evaluation in pancytopenia—excisional biopsy with architectural preservation is required for diagnosing lymphomas and histiocytic disorders. 1

Algorithmic Approach Summary

1. Confirm pancytopenia with CBC and peripheral smear review
2. Assess for hemolysis with reticulocyte count, LDH, haptoglobin, bilirubin
3. Screen for reversible causes: B12, folate, iron studies, HIV, HCV, H. pylori
4. Evaluate medication/exposure history and autoimmune markers if indicated
5. Proceed to bone marrow aspiration AND biopsy with cytogenetics if age >60, blasts present, reticulocyte count <1.5%, systemic symptoms, or diagnosis unclear
6. Obtain urgent hematology consultation for any patient with blasts or when bone marrow examination reveals acute leukemia, high-risk MDS, or severe aplastic anemia 3, 5