Analytical performance of a multiplexed, bead-based cytokine detection system in small volume samples

Background: Multiplexed cytokine measurement offers many advantages over the conventional enzyme-linked immunosorbent assay (ELISA) format when applied in large-scale epidemiological studies or clinical trials. In the present study we set out to define the reliability and consistency of a suspension multiplexed protein array, the cytometric bead array (CBA), in large-scale, longitudinal studies. Methods: The cytokines interleukin (IL)-5, IL-10, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were measured in pediatric samples from childhood asthma and allergy studies. Analytical performance of CBA was determined in sample supernatants and CBA was compared to conventional ELISA. Results: Within-run and total imprecision were between 5.2% -10.8% and 5.6%-13.2%, respectively, at three different concentrations for all cytokines. Slopes of dilution linearity were between 1.01 and 1.31 for the four cytokines. The recovery rate at two different concentrations of the cytokines was between 97% and 113%. Lower limits of detection and quantification as well as functional sensitivity were determined. Comparison of the multiplex array and solid phase method showed good correlation with r between 0.82 and 0.93. The sample volume required for the multiplex format was 25% of the ELISA sample volume. Conclusions: CBA analytical evaluation and comparison to an ELISA format demonstrated high reproducibility, sensitivity and good applicability for small volume samples.