The Immunopathology laboratory will begin offering flow cytometric testing for Zap-70 for patients with Chronic Lymphocytic Leukemia (CLL) on July 11, 2005.  The expression level of Zap-70 in CLL cells provides important prognostic information.  Patients with high level Zap-70 expression exhibit a more aggressive clinical course.^{1, 2} 

Unfortunately, Zap-70 is a very labile cytoplasmic protein.  As a result, fresh peripheral blood specimens must be used for the determination.  In addition, the test is also more labor intensive than routine flow cytometry.  Because of these limitations, acceptable specimens for Zap-70 testing will need to meet the following criteria:

1.) Patients must have either a definite or a strong presumptive diagnosis of chronic lymphocytic leukemia.  The test will generally not be run on a specimen if CLL is only part of a broader differential diagnosis.

Zap-70 has only been shown to be of value in cases of chronic lymphocytic leukemia.

2.) A fresh peripheral blood specimen in ACD-A anticoagulant (yellow top tube) must be received by the Immunopathology Laboratory within a maximum of 6 hours of being drawn.  Bone marrow and tissue specimens are not acceptable.

ZAP-70 levels decrease rapidly after blood has been drawn.  Optimum quantitation is achieved if testing occurs within 8-12 hours; after 12 hours the test results are invalid. The assay has not been validated for bone marrow and other tissues.

3.) Testing days are Monday through Friday with a cut off time at 2:30 p.m.

Due to the complex nature of this test and its time requirements, it cannot be performed outside of routine lab hours.  The 2:30 p.m. cutoff time allows completion of the test during routine laboratory hours.

4.) Notification of the Laboratory prior to sending the specimen is desirable.

Optimally, ZAP-70 analysis should be scheduled with the lab when the patient visit is arranged/scheduled and specimens should be delivered directly to Immunopathology Lab (5238 RCP).

References:
  1.) N Engl J Med 2003; 348:1764-75
  2.) LANCET 2004; 363:105-11