ZAP-70 Protein Expression in B-cell Chronic Lymphoid Leukemia: a Single Center Experience from Pakistan

Background: Chronic lymphoid leukemia (CLL) is the most frequent type of adult leukemia. The Rai and Binet staging systems have been well recognized as standards for assessing the treatment requirements and overall survival in CLL patients. However, there is a need to seek newer prognostic markers to identify stable or progressive forms of CLL that will facilitate risk-adapted treatment strategies. Currently a molecular biomarker ZAP-70 has attracted interest as providing prognostic information in CLL patients. Objective: To determine the frequency of ZAP-70 positivity in B-CLL patients at disease presentation. Materials and Methods: From January 2011 to September 2014, 89 patients were diagnosed to have chronic lymphoid leukemia. Complete blood count was done on an automated analyzer (Cell Dyne, Abott Architect, USA), while immunophenotyping was conducted for each patient to establish the diagnosis of the disease. ZAP-70 expression was evaluated by flow cytometry. Data were compiled and analyzed by SPSS version 21. Results: Out of the total of 89 B-CLL patients, 62 (69.7%) were male and 27 (30.3%) were females with a male to female ratio of 2:1. The mean age was $57.5{\pm}12.1years$. The frequency of ZAP-70 positivity in our B-CLL patients was found to be 13.5%. ZAP-70 positivity was significantly correlated with stage III disease and high absolute lymphocytic count (P<0.05). No correlation of ZAP-70 could be established with age and gender (p>0.05). Conclusions: The frequency of ZAP-70 in our patients appears low. It is approximately half that in international data. We would recommend to screen all the newly diagnosed patients with CLL for ZAP-70 protein expression for risk stratification, family counseling and to predict overall survival.