From the Guidelines
Classic lab findings for chronic lymphocytic leukemia (CLL) include an elevated white blood cell count with a predominance of small, mature-appearing lymphocytes in the peripheral blood, absolute lymphocytosis with more than 5,000 lymphocytes/μL, and a monoclonal B-cell population expressing CD19, CD20 (dim), CD23, and CD5, with light chain restriction. The diagnosis of CLL is established by the presence of ≥5000 B lymphocytes/µl in the peripheral blood for the duration of at least 3 months, as stated in the study by 1. Key laboratory findings include:
- Elevated white blood cell count (typically >10,000/μL) with a predominance of small, mature-appearing lymphocytes in the peripheral blood
- Absolute lymphocytosis with more than 5,000 lymphocytes/μL
- Flow cytometry revealing a monoclonal B-cell population expressing CD19, CD20 (dim), CD23, and CD5, with light chain restriction (either kappa or lambda)
- Low levels of surface immunoglobulin
- Bone marrow examination typically showing >30% lymphocytes
- Anemia and thrombocytopenia may be present in advanced disease
- Hypogammaglobulinemia is common, especially as the disease progresses, leading to increased infection risk
- Elevated beta-2 microglobulin and lactate dehydrogenase (LDH) levels may indicate more aggressive disease
- Cytogenetic abnormalities detected by FISH, such as del(13q), del(11q), del(17p), and trisomy 12, provide important prognostic information, as mentioned in the study by 2. These findings reflect the underlying pathophysiology of CLL, which involves the accumulation of monoclonal B lymphocytes due to defective apoptosis rather than increased proliferation.
From the Research
Classic Laboratory Findings for Chronic Lymphocytic Leukemia (CLL)
The classic laboratory findings for CLL are characterized by a specific immunophenotype, which includes:
- Expression of CD5, CD19, dim CD20, dim CD22, CD23, bright CD43, dim CD45, dim to negative CD79b, dim CD81, CD200, and dim monoclonal surface immunoglobulin 3
- A characteristic combination of markers that differentiates CLL from other mature B-cell neoplasms (MBCN), including CD19+ CD20(+low) CD22(+low) CD5(+high) CD23+ FMC7- CD79b(+low) sIg(+low) 4
- The presence of ≥5000 clonal B-lymphocytes/μL, coexistence of CD19, CD20, CD5, and CD23, restriction of light chain immunoglobulin, and lack of expression of antigens CD22 and CD79b 5
Immunophenotypic Profile
The immunophenotypic profile of CLL cells is distinct from other lymphoproliferative disorders, with a typical phenotype characterized by:
- CD5+, CD23+, FMC7-, weak expression of surface Ig (sIg), and weak or absent expression of membrane CD22 and CD79b 6
- Lower antibody binding capacity (ABC) levels for CD19, CD20, CD22, and CD79b, compared to normal controls 7
Diagnostic Criteria
The diagnosis of CLL requires the presence of a characteristic immunophenotype, as well as other diagnostic criteria, including:
- Morphological features, such as the presence of small, mature-appearing lymphocytes with a characteristic "halo" around the nucleus 6
- Clinical features, such as lymphadenopathy, splenomegaly, and fatigue 6
- Molecular genetics, such as the presence of specific chromosomal abnormalities, including trisomy 12 and deletions of 13q14 5, 6