A study by Ray and co. used a multiplex immunoassay to look for five cytokines in human blood. Cytokines are molecules that are involved in many biological processes, including inflammation and cell differentiation, and the levels of these cytokines present in blood plasma can vary as part of a disease process.

Sepsis is one such disease that is characterized by a change in the levels of cytokines that promote inflammation (pro-inflammatory cytokines), such as IL-1β, TNFα, IL-6, and IL-8. Cytokine levels can also be changed in response to certain compounds, some of which are being investigated as potential therapeutic drugs. Therefore, it is beneficial to have a system where the levels of multiple cytokines can be analyzed at once; this is what Ray and co. intended to do. Here, they developed an assay which could identify levels of IL-1β, TNFα, IL-6, IL-8, and IL-10.

Using a bead-based method, each bead had capture antibodies for the above cytokines and were distinguished by the ratio of dye added. The authors were able to detect concentration of these cytokines while using a limited amount of patient blood sample, and at a reduced cost.