Preliminary report on cytokine determination in human synovial fluids: a consensus study of the European Workshop for Rheumatology Research. The Cytokine Consensus Study Group of the European Workshop for Rheumatology Research.

A consensus study involving several European research groups was conducted in order to assess the reliability and reproducibility of cytokine measurements in biological fluids. Six synovial fluids and one serum--some of them spiked with recombinant human cytokines--were aliquoted and distributed blindly to different laboratories. The samples were tested for tumor necrosis factor alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha) and 1 beta, IL-6, IL-2, interferon gamma (IFN-gamma), and the soluble receptors of IL-2 (IL-2R) and TNF (TNF-sR55 and -sR75), using various immunoassays and, occasionally, bioassays. The same ELISA used in different laboratories yielded comparable results, whereas different ELISAs usually detected the highest levels in the same samples, but yielded different absolute values. This finding highlights the necessity of establishing international standards for all immunoassays. Many other questions arose during this preliminary study, and further investigations are planned to clarify them.