Early detection of bladder cancer is crucial for improved patient outcomes, as patients see a sharp decline in 5-year survival rate from 80% to < 35%, at early or late stage diagnosis of the disease respectively. Gene expression studies indicated L-selectin (CD62L) as a potential protein biomarker indicative of metastatic bladder cancer. Here, a quantitative bead-based microfluidic immunoarray for CD62L expression in human serum is described. Sandwich immunoassay is established by surface binding of primary antibody on an 8-electrode carbon array and magnetic beads decorated with multiple detection antibodies and horseradish peroxidase enzyme-labels. Electrochemical detection is conducted by injecting a hydroquinone/hydrogen peroxide activator/mediator mixture for amperometric signal detection. Our analysis of 40 patient samples shows an overall increase in CD62L concentration with progression of disease stage. A drop-off in soluble CD62L is seen for late stage, high-grade metastatic tumors. In-depth statistical analysis is conducted to examine the comparative performance of traditional immunoassay and our modified immunoarray for CD62L.