Chronic lymphocytic leukemia (CLL) is a heterogeneous disease. Many patients never need treatment, whereas others have an aggressive clinical outcome with significantly reduced median survival. New treatments that can induce complete remission permit patients with poor outlook to be treated while they are still asymptomatic. However, asymptomatic patients with low tumor burden (Binet stage A) derive no benefit from treatment and should be spared the unnecessary ordeal and expense. The problem is how to distinguish those patients with aggressive disease and who are candidates for treatment from those with indolent disease who are not. ZAP-70 is an intracellular protein that is expressed in T-cells and natural killer cells, but absent in B-cells of healthy people. First evidence that presence of ZAP-70 in B-cells of patients with aggressive form of CLL was identified by Rosenwald et al. in 2001 and verified by Wiestner et al. in 2003. ZAP-70 present in B-cells is a biomarker that can accurately differentiate these two patient groups and, thus, a very important prognostic indicator. Current test methods are either not widely available or insufficiently standardized. In Phase I, we demonstrated that the Integrating Waveguide Biosensor technology can be used to detect very low concentrations of proteins and cells in buffer and various matrices by sandwich immunoassay and fluorescence detection. Detection is rapid, as fast as 20 minutes, and quantitative. In this Phase II SBIR, we will apply the biosensor to detection of ZAP-70 in B cells of patients who have been diagnosed with CLL. The level of ZAP-70 so detected will provide useful and sought-after information for physicians and patients in order to understand the stage of CLL disease and determine the appropriate timing and choice of treatment, and to confirm post-treatment minimal residual disease. Assays, instrument, and a test cartridge will be developed and tested against blood specimens from CLL patients and controls. The most common human leukemia is B-cell chronic lymphocytic leukemia (CLL). Patients with a slowly progressive subtype of CLL may have a normal life span and may never require treatment. Patients with the more rapidly progressive form of CLL typically progress to symptomatic disease and need chemotherapy. The principle of delaying chemotherapy until the disease has progressed is founded on the observation that chemotherapy given to all patients at diagnosis is not beneficial to all. ZAP-70 in B-cells was found to be a reliable marker of disease progression. This proposal will develop a sensitive detection for ZAP-70 in B-cells to allow the doctor to identify the patients with aggressive form of CLL and provide treatment immediately. [unreadable] [unreadable] [unreadable]