Cytometric bead assay of cytokines in sepsis: a clinical evaluation

The clinical relevancy of an attractive new multiparametric method, cytometric beads assay (CBA), was evaluated for the monitoring of cytokines in sepsis.

A total of 52 samples (26 patients) were simultaneously tested by CBA and chemiluminescence (IL-6, IL-8, IL-1beta, and TNFalpha) or ELISA (IL-10, IL-12 p40, IL-12 p70, and soluble TNFalpha-RI).

CBA standard curves were linear from 20-5,000 ng/L except for IL-1beta (40-5,000 ng/L). IL-6 and IL-8 were detected in 41 and 48 samples (44-5,000 ng/L and 22-5,000 ng/L), respectively, and out of range in six samples. IL-10 and IL-1beta were detected in 14 and 15 samples (21-1,548 ng/L and 29-582 ng/L), respectively. TNFalpha was rarely detected, and IL-12 p70 was never detected. Accuracy and repeatability were good (CV for IL-6 was 2.1-8.7%; for IL-8 3.7-5.3%; for IL-10 2.5-9.1%; for IL-12 5.2-6.5%; for IL-1 beta 4-12%; and for TNFalpha 3-19.3%). Reproducibility of four standard curves and 20 samples (-1.1 to +1.03%) was excellent between tests done at two- to six-week intervals. CBA values were correlated (r2 > 0.89; P < 0.001) with our reference methods, but were lower on CBA (TNFalpha 45% +/- 8; IL-6 49% +/- 7), probably due to interactions with patients' serum, as confirmed by spiking diluted standards in one patient's serum with end stage renal failure and high levels of TNF soluble receptor (i.e., TNFalpha levels 34 and 21%).

Finally, these results suggest that IL-6, IL-8, IL-1beta, and Il-10 are clinically promising for sepsis evaluation. However, sensitivity of TNFalpha has to be improved and IL-12 p70 should be replaced with more relevant parameters such as TNF-R, procalcitonin, or neopterin.