From the Guidelines
The most common lab findings in leukemia subtypes are highly variable and depend on the specific form of leukemia, with recent guidelines emphasizing the importance of comprehensive diagnostic workups, including complete blood counts, peripheral blood smears, bone marrow aspiration and biopsy, flow cytometry, and cytogenetic testing, as outlined in the 2019 ASCO clinical practice guideline endorsement of the College of American Pathologists and American Society of Hematology guideline 1.
Key Laboratory Findings by Leukemia Subtype
- Acute Myeloid Leukemia (AML): pancytopenia, blast cells in peripheral blood, and Auer rods on microscopy
- Acute Lymphoblastic Leukemia (ALL): lymphoblasts in peripheral blood, thrombocytopenia, and elevated LDH levels
- Chronic Myeloid Leukemia (CML): marked leukocytosis with a left shift, basophilia, low leukocyte alkaline phosphatase, and the Philadelphia chromosome (BCR-ABL fusion)
- Chronic Lymphocytic Leukemia (CLL): lymphocytosis (>5,000/μL), smudge cells on blood smear, and CD5+/CD23+ B-cells on flow cytometry
- Hairy Cell Leukemia: pancytopenia with characteristic "hairy cells" on peripheral smear and positive TRAP staining
Essential Diagnostic Components
- Complete blood counts with differential
- Peripheral blood smears
- Bone marrow aspiration and biopsy
- Flow cytometry
- Cytogenetic testing, including conventional karyotyping and FISH, as recommended in the 2019 guideline 1
Additional Considerations
- Molecular studies, such as PCR and RT-PCR, may be necessary for certain subtypes of leukemia, as outlined in the 2019 guideline 1
- Immunophenotyping is crucial for the diagnosis of B- or T-ALL, AML, or MPAL, and should be performed on bone marrow aspirate or peripheral blood, as recommended in the 2019 guideline 1
From the Research
Common Lab Findings in Leukemia Subtypes
- Leukocytosis is a common finding in leukemia, as noted in 2
- A complete blood count usually reveals leukocytosis and other abnormally elevated or depressed cell lines, as stated in 3
- The diagnosis of leukemia is confirmed by further examination of the bone marrow or peripheral blood, as mentioned in 3
Acute Lymphoblastic Leukemia (ALL) Lab Findings
- Pediatric-type ALL chemotherapy regimens have led to improved outcomes for children, adolescents, and young adults with ALL, as discussed in 4
- BCR-ABL-targeting tyrosine kinase inhibitors (TKIs) have improved outcomes in Philadelphia chromosome-positive (Ph+) ALL, as noted in 4
Chronic Myeloid Leukemia (CML) Lab Findings
- CML can progress to an accelerated or blast phase if left untreated or inadequately managed, as described in 5
- Acute transformation of CML, particularly into mixed lineage leukemia, is a rare and challenging complication, as reported in 5
- BCR-ABL1 fusions were p210 in 25 patients and p190 in 3 patients with CML-LBC, as found in 6
Acute Myelogenous Leukemia (AML) Lab Findings
- AML-M2a was confirmed by bone marrow analysis, flow cytometry, and cytogenetics showing BCR-ABL1 positivity in a patient with CML progressing to acute mixed lineage leukemia, as described in 5
- Patients with CML-LBC had higher leukocyte and absolute neutrophil counts, higher immature myeloid cells in peripheral blood, and lower blast counts compared to patients with Ph+ B-ALL, as noted in 6