Detection of ZAP-70 in patients with chronic lymphocytic leukemia.

PURPOSE: To determine the presence and prognostic significance of ZAP-70 in patients with B chronic lymphocytic leukemia (B-CLL). Expression of ZAP-70 in B-CLL is a continuum ranging from absent to high, affecting the prognostic reliability of this marker. PATIENTS AND METHODS: 32 patients with B-CLL treated from March 2006 to February 2007 were prospectively studied. Patients were stratified in two groups: those diagnosed with B-CLL within 18 months and a retrospective group diagnosed before 18 months since the beginning of this study. Patients were predominantly males (78.1%), over 60 years old (81.25%). ZAP-70 was detected on EPICX-XL flow cytometer with System II software. Directly conjugated antibodies CD19 PE, ZAP-70 FITC (clone 1E7.2) and CD2 APC were used. Leuoperm was used for permeabilization. All samples with over 20% ZAP-70/CD19 double positive B lymphocytes were considered positive. RESULTS: ZAP-70 was absent in a group of 22 patients with B-CLL diagnosed over 18 months from the beginning of this study, while 2 out of 10 (20%) patients from the group of newly diagnosed patients were ZAP-70(+). During follow up both ZAP-70(+) cases showed worsening of their clinical status resulting to death in one patient. In borderline cases with ZAP-70(+) ranging from 10.9-19.9% there was no correlation of the level of ZAP-70 expression with disease activity or clinical scoring systems. CONCLUSION: Very high percentage of ZAP-70(+) cells is a sign of poor prognosis in B-CLL. Borderline expression of ZAP-70, although more frequent, could not be successfully assigned into a risk group.