Electronic Immunoaffinity Assay for Differential Leukocyte Counts

Leukocytes are blood cells involved in the immune response. Leukocytes can be classified into three main groups (granulocytes, lymphocytes, and monocytes), and the measurement of the relative prevalence of each subgroup, termed differential leukocyte count, is an important clinical parameter in the diagnosis and prognosis of various health anomalies. Currently, differential leukocyte counts are obtained either manually through labor-intensive blood smears or by employing bulky hematology analyzers. Both of these measurements require a laboratory setup and hence are not amenable for decentralized and point-of-care settings. In this paper, we introduce a microfluidic assay with an electronic readout for differential leukocyte count assays. Our device classifies leukocyte subgroups based on the differential CD33 expression on cell membranes. In the device, each subgroup is differentially immunocaptured in different microfluidic chambers, while the cell capture rates are quantified by an integrated electronic sensor network. When benchmarked against a commercial hematology analyzer, our device could identify leukocyte subpopulations with differences of <; 6% for granulocytes and lymphocytes, and a <; 3% for monocytes. These results demonstrate the potential of our technique as an accurate method to perform the widely-employed hematology assay for point-of-care applications without the need for sample labeling.