What is the initial diagnostic work‑up for a patient with unexplained cytopenias, fatigue, bruising, bleeding, weight loss, night sweats, lymphadenopathy, or organomegaly to evaluate for possible leukemia?

Diagnostic Work-Up for Suspected Leukemia

When evaluating a patient with unexplained cytopenias, constitutional symptoms (fatigue, weight loss, night sweats), bleeding/bruising, lymphadenopathy, or organomegaly, immediately obtain a complete blood count with differential and peripheral blood smear, followed by urgent hematology-oncology referral if leukemia is suspected. 1

Initial Clinical Assessment

Obtain and document the following clinical information before pathology evaluation:

• Patient demographics: Age, sex, ethnicity 1
• Hematologic history: Any prior blood disorders, known predisposing conditions or genetic syndromes, family history of hematologic malignancies 1
• Exposure history: Prior chemotherapy, immunotherapy, radiation therapy, or toxic substance exposures 1
• Confounding factors: Recent growth factor therapy, transfusions, or medications that may obscure leukemia features 1
• Physical examination findings: Neurologic examination, presence/absence of lymphadenopathy, hepatomegaly, splenomegaly 1, 2

Laboratory Diagnostic Algorithm

Step 1: Initial Blood Work (Immediate)

• Complete blood count with differential to identify cytopenias, leukocytosis, or abnormal cell populations 3, 4, 5
• Peripheral blood smear examination by a qualified hematologist/pathologist to identify blast cells, abnormal lymphocytes, or other morphologic abnormalities 2, 3, 5
• Lactate dehydrogenase (LDH) as an indicator of cell turnover in hematologic malignancies 3
• Comprehensive metabolic panel including bilirubin 2
• Direct antiglobulin test (DAT) to evaluate for autoimmune hemolysis 2

Step 2: Confirmatory Testing for Acute Leukemia

Four traditional techniques form the backbone of acute leukemia diagnosis: 1

1. Cytomorphology - Microscopic examination of cell structure 1
2. Cytochemistry - Special staining to identify cell lineage 1
3. Immunophenotyping by multiparameter flow cytometry - Essential for determining lineage (lymphoid vs. myeloid) and subtype classification 1
4. Molecular and cytogenetic studies - Including FISH and karyotyping for risk stratification 1

Step 3: Bone Marrow Evaluation

Bone marrow aspiration and biopsy are crucial when acute leukemia is suspected, with the following analyses: 3

• Morphologic evaluation to assess blast percentage and cellularity 3
• Flow cytometry to identify lymphoproliferative disorders and characterize cell populations 3
• Cytogenetics to detect clonal abnormalities (particularly del(17p), del(11q), t(11;14)) 2, 3
• Immunohistochemistry for further characterization 3
• Next-generation sequencing (NGS) for molecular markers important in risk stratification and targeted therapy 1

Step 4: Chronic Lymphocytic Leukemia (CLL) Specific Criteria

For suspected CLL, diagnosis requires: 2

• Sustained peripheral blood lymphocytosis ≥5×10⁹/L for at least 3 months not explained by other disorders 2
• Characteristic immunophenotype by flow cytometry: CD5+, CD19+, CD20+ (low), CD23+, surface immunoglobulin low, CD79b low, FMC7 negative 2
• Physical examination with careful palpation of all lymph node areas, spleen, and liver 2

Note: Monoclonal B lymphocytosis (MBL) is diagnosed when monoclonal B lymphocytes are <5×10⁹/L without lymphadenopathy, organomegaly, or cytopenias 2

Additional Imaging and Studies

• CT scan of chest, abdomen, and pelvis to evaluate for lymphadenopathy, splenomegaly, hepatomegaly, or other organomegaly 3
• HIV and hepatitis C testing given constitutional symptoms with cytopenias 3
• Tuberculosis evaluation (chest imaging, tuberculin skin testing, or interferon-gamma release assay) as TB can mimic leukemia presentation 3
• SARS-CoV-2 screening in all patients with hematological malignancies and fever 3

Critical Pitfalls to Avoid

Do not delay hematology-oncology referral while awaiting test results - patients with suspected leukemia require prompt specialist evaluation 4, 5

Do not use absolute lymphocyte count alone as an indicator for CLL treatment - leukostasis rarely occurs in CLL unlike acute leukemias 6

Do not routinely administer G-CSF until the underlying diagnosis is established - this may exacerbate inflammatory injury and obscure diagnosis 3

Do not dismiss musculoskeletal symptoms - bone pain, limb pain, and joint pain are common presenting features in childhood leukemia and may initially be misdiagnosed as arthritis or osteomyelitis 7, 8

Recognize that 6% of leukemia patients are asymptomatic at diagnosis and blood counts may initially be subtle or within normal limits 1, 7

Infection Management During Work-Up

If fever is present with neutropenia, initiate empirical broad-spectrum antibiotics promptly before completing the diagnostic work-up 3