From the Guidelines
Diagnosing Chronic Lymphocytic Leukemia (CLL) on peripheral blood flow cytometry requires the presence of at least 5 x 10^9/L monoclonal B-lymphocytes and confirmation of clonality by flow cytometry, as stated in the NCCN clinical practice guidelines 1. To diagnose CLL, the following criteria should be met:
- Presence of ≥5 x 10^9/L monoclonal B-lymphocytes in the peripheral blood
- Clonality of B cells confirmed by flow cytometry
- Characteristic immunophenotypic features, including co-expression of CD19, CD5, and CD23, along with dim expression of surface immunoglobulin (sIg) The diagnosis can be established through flow cytometry of peripheral blood with immunophenotyping using cell surface markers, and bone marrow biopsy is generally not required 1. Key markers to assess include:
- CD19
- CD5
- CD23
- Surface immunoglobulin (sIg)
- CD20
- Kappa or lambda light chains to confirm monoclonality Additional testing, such as FISH analysis for chromosomal abnormalities, may be performed for prognostic stratification 1. It's worth noting that the 2015 ESMO clinical practice guidelines also support the diagnosis of CLL based on the presence of ≥5000 monoclonal B lymphocytes/µl in the peripheral blood and confirmation of clonality by flow cytometry 1, however, the most recent and highest quality study 1 is preferred for guiding clinical practice.
From the Research
Diagnosis of CLL using Peripheral Flow Cytometry
To diagnose Chronic Lymphocytic Leukemia (CLL) using peripheral flow cytometry, several markers and their expression patterns are considered. The following points highlight the key findings:
- CLL has a characteristic immunophenotype that can be identified by flow cytometry, including the expression of CD5, CD19, dim CD20, dim CD22, CD23, and dim monoclonal surface immunoglobulin 2.
- The combination of markers CD19+ CD20(+low) CD22(+low) CD5(+high) CD23+ FMC7- CD79b(+low) sIg(+low) is highly suggestive of CLL 3.
- CD5 and CD23 are highly expressed in CLL, while FMC7 is typically negative 3, 4.
- The intensity of CD20 expression is lower in CLL compared to other B-cell disorders, and FMC7 is of greater diagnostic value than CD20 for distinguishing CLL from other B-cell disorders 4.
- Flow cytometry is an effective tool for diagnosing CLL, and its results can be correlated with immunohistochemistry findings 5.
Markers for CLL Diagnosis
Some key markers used in the diagnosis of CLL include:
- CD5: highly expressed in CLL 3, 2
- CD19: expressed in CLL, but with lower intensity than in other B-cell disorders 3, 2
- CD20: dimly expressed in CLL, with lower intensity than in other B-cell disorders 3, 2, 4
- CD22: dimly expressed in CLL 3, 2
- CD23: highly expressed in CLL 3, 2
- FMC7: typically negative in CLL 3, 4
- CD79b: dimly expressed in CLL 3, 2
- sIg: dimly expressed in CLL, with lower intensity than in other B-cell disorders 3, 2
Diagnostic Approach
The diagnostic approach for CLL using peripheral flow cytometry involves:
- Analyzing the expression of various markers, including CD5, CD19, CD20, CD22, CD23, FMC7, CD79b, and sIg 3, 2
- Evaluating the intensity of marker expression, as well as the presence or absence of specific markers 3, 2, 4
- Correlating flow cytometry results with clinical and laboratory findings, including immunohistochemistry results 5