Blood Work Findings in Leukemia
Blood work in leukemia typically shows abnormal white blood cell counts (either elevated or decreased), presence of immature blast cells in peripheral blood, and often accompanying anemia and thrombocytopenia, with specific patterns varying by leukemia subtype. 1
Essential Initial Laboratory Evaluation
The complete blood count (CBC) with differential and peripheral blood smear review is the essential first diagnostic step when leukemia is suspected. 1 At least 200 leukocytes should be counted on blood smears using May-Grünwald-Giemsa or Wright-Giemsa staining. 2
Acute Myeloid Leukemia (AML) Blood Findings
For AML diagnosis, a blood blast count of 20% or more is required in most cases, with myeloblasts, monoblasts, or megakaryoblasts present in the peripheral blood. 2, 1
Key blood work abnormalities include:
- Presence of myeloblasts, monoblasts, or megakaryoblasts in peripheral blood 1
- Anemia (hemoglobin typically decreased) 1
- Thrombocytopenia (platelet count typically decreased) 1
- Variable white blood cell count (can be elevated, normal, or decreased) 3
Hyperleukocytosis in AML
Approximately 18% of AML patients present with white blood cell counts greater than 100,000/μL, a condition called hyperleukocytosis. 4 This is particularly common in patients with monocytic or myelomonocytic differentiation. 5 Hyperleukocytosis carries increased risk of leukostasis, tumor lysis syndrome, and disseminated intravascular coagulation. 6, 5, 4
Chronic Myeloid Leukemia (CML) Blood Findings
CML presents with distinctly different blood work patterns:
- Leukocytosis with basophilia 1
- Immature granulocytes including metamyelocytes, myelocytes, and promyelocytes with few myeloblasts 1
- Thrombocytosis may be present 1
- White blood cell count often markedly elevated but symptoms of leukostasis rarely occur despite high counts 2
Chronic Lymphocytic Leukemia (CLL) Blood Findings
For CLL, the peripheral blood shows:
- Absolute lymphocyte count elevation with both percentage and absolute number of lymphocytes documented 2
- Lymphocyte doubling time is an important prognostic indicator 2
- The absolute lymphocyte count should not be used as the sole indicator for treatment but included as part of the total clinical picture 2
Plasma Cell Leukemia Blood Findings
Plasma cell leukemia requires specific blood findings:
- Plasma cells greater than 5% in peripheral blood by flow cytometry for diagnosis 2
- At least 200 leukocytes on blood smears should be counted 2
- Hemoglobin less than 10 g/dL in over 50% of cases 2
- Platelet count less than 100,000/μL in over 50% of cases 2
Additional Laboratory Studies
Beyond the CBC, initial blood work should include:
- Comprehensive metabolic panel to monitor for tumor lysis syndrome 2
- Lactate dehydrogenase (often elevated, particularly with high tumor burden) 2
- Uric acid and phosphate levels (important for tumor lysis syndrome risk) 2
- Coagulation panel including prothrombin time, partial thromboplastin time, and fibrinogen activity to detect disseminated intravascular coagulation, particularly in acute promyelocytic leukemia 2
Critical Pitfalls to Avoid
Recent growth factor therapy, transfusions, or certain medications can obscure or mimic features of acute leukemia, so medication history must be carefully documented. 1
Leukostasis is rarely diagnosed with high confidence despite characteristic clinical presentations, so high clinical suspicion is needed when white blood cell counts exceed 100,000/μL, particularly in AML with monocytic differentiation. 6
The peripheral blood may be adequate for diagnosis when sufficient blasts are present, avoiding the need for bone marrow biopsy in unstable patients or those with contraindications. 2 Manual differential count, flow cytometry, and molecular studies can be performed on peripheral blood specimens if adequate blasts are present. 2