What investigation is routinely required to establish a diagnosis of chronic lymphocytic leukemia?

What investigation is routinely required to establish a diagnosis of chronic lymphocytic leukemia?

• A. Flow cytometry and immunophenotyping of peripheral blood
• B. Bone marrow biopsy and cytogenetics
• C. Serum protein electrophoresis
• D. Peripheral blood smear review only

Answer: (A)

Diagnosing chronic lymphocytic leukemia relies on identifying a clonal B-cell population with the characteristic immunophenotype on flow cytometry. Peripheral blood flow cytometry shows B cells that express CD5 and CD23 together with CD19 and a dimmer CD20, along with restricted surface light chains, which together confirm the CLL clone. This immunophenotypic pattern distinguishes CLL from reactive lymphocytosis and other small B-cell disorders, making this test routinely necessary to establish the diagnosis. Bone marrow biopsy and cytogenetics can provide prognostic or staging information and may be used in certain cases, but they are not required to confirm the diagnosis. Serum protein electrophoresis is not relevant to diagnosing CLL. A peripheral blood smear can raise suspicion by showing mature-appearing lymphocytes (and sometimes smudge cells), but it cannot establish clonality or the specific immunophenotype needed for diagnosis.

Diagnosing chronic lymphocytic leukemia relies on identifying a clonal B-cell population with the characteristic immunophenotype on flow cytometry. Peripheral blood flow cytometry shows B cells that express CD5 and CD23 together with CD19 and a dimmer CD20, along with restricted surface light chains, which together confirm the CLL clone. This immunophenotypic pattern distinguishes CLL from reactive lymphocytosis and other small B-cell disorders, making this test routinely necessary to establish the diagnosis.

Bone marrow biopsy and cytogenetics can provide prognostic or staging information and may be used in certain cases, but they are not required to confirm the diagnosis. Serum protein electrophoresis is not relevant to diagnosing CLL. A peripheral blood smear can raise suspicion by showing mature-appearing lymphocytes (and sometimes smudge cells), but it cannot establish clonality or the specific immunophenotype needed for diagnosis.