Chronic Lymphocytic Leukemia (CLL) - Diagnostic and Prognostic Testing

The CLL/Lymphoma Diagnostic Panel (test code 17817[X]) is a flow cytometry test that can be performed using blood, bone marrow aspirate, or fresh tissue. In addition to standard B-cell and T-cell markers, it includes CD38 and FMC7, which assist in the differential diagnosis of other B-cell lymphoproliferative disorders.

The CLL Prognostic Panel, Comprehensive (test code 17239) can be used for determining prognosis and risk stratification. It includes chromosome analysis, a 6-marker FISH panel, IgV_H gene mutation analysis, ZAP-70, CD38, and serum ß2-microglobulin. This test code includes a patient-specific overall risk categorization based on all the test results.

Each of these markers can also be ordered individually. Please refer to our Directory of Services for ordering information.

CLL can have widely variable outcomes, and clinical management is dependent on the presenting features and disease course. Molecular and immunophenotypic markers can help identify those patients with a higher risk for aggressive disease.^1-4 This can help physicians select the optimal treatment and surveillance program at time of initial diagnosis.^3,4

The most important predictor of adverse outcome and a need for treatment is deletion/loss of the TP53 gene.³ Other strong predictors of more aggressive disease include unmutated IgV_H status, ZAP-70 expression, and deletion/loss of the ATM gene.¹ Less significant predictors of poor outcome include elevated ß2-microglobulin and increased CD38 expression (≥30% of CD5+/CD19+ cells).

Note that the presence of del13q14 and/or trisomy (+)12, which may be detected by chromosome analysis or FISH, is not associated with an unfavorable prognosis but can be helpful in establishing a diagnosis of CLL in cases with atypical features.

Many cases of high-risk CLL have abnormal results for several prognostic markers. Few cases, however, demonstrate presence of all the unfavorable markers. Furthermore, multiple, large studies have shown that although some unfavorable markers are closely correlated to each other, most still have independent prognostic power in multivariate models.¹ Consideration of favorable and unfavorable markers and their relative prognostic power provides the most complete picture of a patient’s risk for aggressive disease. In the comprehensive prognostic panel (test code 17239), a patient-specific interpretation that considers the relative prognostic power of the markers detected is provided.

Either blood or bone marrow aspirate samples from a patient with CLL can be tested. This panel should NOT be ordered if the sample shows minimal involvement by CLL. Consider ordering test code 17817[X] instead for workup of patients with possible low-levels of residual CLL. 

ZAP-70 is a membrane-associated, intracellular protein kinase that is critical for signal transduction in T-cells and natural killer (NK)-cells. It is not normally present in B-cells.

Aberrant ZAP-70 expression in ≥10% of CD5+/CD19+ cells has been shown to be an unfavorable CLL prognostic indicator.² Patients with CLL and a positive ZAP-70 test result tend to have an unmutated IgV_H gene, unfavorable cytogenetic features, and a shorter time interval from diagnosis to treatment. In contrast, a negative result, indicated by ZAP-70 expression in <10% of CD5+/CD19+ cells, is associated with more favorable features, such as mutated IgV_H and no evidence of ATM and TP53 genetic loss. 

Flow cytometric measurement of intracellular ZAP-70 requires a robust technique.⁵ In our assay, the expected levels of ZAP-70 positivity in T-cells and NK-cells and the absence of staining in non-neoplastic B lymphocytes (when present) are used as internal controls. ZAP-70 expression is reported only in the CD5+/CD19+ cells. 

If only formalin-fixed, paraffin-embedded (FFPE) bone marrow tissue is available, we can test for ZAP-70 expression using immunohistochemistry (ZAP-70, IHC with Interpretation, test code 90192). Our studies using parallel FFPE tissue and bone marrow aspirate material show that IHC results correlate well with flow cytometry results. Other prognostic factors, such as karyotype, FISH markers, CD38 and ß2-microglobulin levels, are not available on FFPE material.