A rapid enzyme-linked immunosorbent assay with two modes of detection for measuring cytokine concentration

Interleukin (IL)-6 and IL-8 were measured in 101 serum samples collected from eight intensive-care unit patients using a polystyrene-based stick enzyme-linked immunosorbent assay (STICKELISA) system. This system consisted of an immobilized-antibody ELISA stick and a noncontact spectrophotometer. Cytokine concentration was detected by two ways: first, rapidly and semi-quantitatively by naked-eye observation of the color change and second, quantitatively using the spectrophotometer for accurate concentration determination. The spectrophotometric assay enabled the quantitation of as little as 100 pg/mL cytokine and took only 45 min to complete. There was a good agreement between the STICKELISA observations and data obtained using a plate ELISA system. The agreement between STICKELISA naked-eye observation and plate ELISA determination was 94 and 85% for IL-6 and IL-8, respectively. The correlation coefficients between the STICKELISA spectrophotometric determination and plate ELISA determination were 0.88 and 0.91 for IL-6 and IL-8, respectively, in a 0.1-5 ng/mL cytokine concentration range. These results demonstrate that the STICKELISA system is a simple, rapid, and quantitative method for bedside cytokine measurement in critical-care settings.