ASSAYING TUMOR-NECROSIS-FACTOR CONCENTRATIONS IN HUMAN SERUM - A WHO INTERNATIONAL COLLABORATIVE STUDY

A collaborative study involving several international research groups was conducted in order to test the validity and reproducibility of tum or necrosis factor-alpha (TNF) measurements in serum. 58 serum samples , nine of them spiked with recombinant human TNF, were aliquoted and d istributed blindly to 11 different laboratories. 20 samples were obtai ned from cerebral malaria patients, 20 from septic shock patients, eig ht from patients with rheumatoid arthritis and ten from normal blood d onors. The serum samples were assayed for TNF using various immunoassa ys (ELISA), radioimmunoassays (RIA) and bioassays. Interassay coeffici ent of variance was analysed. Substantial differences were observed on terms of sensitivity and results obtained with the different commerci al and in-house assays. The level of sensitivity was highest with ELIS As and bioassays. RIAs yielded the highest concentrations of TNF in th e same samples as compared to those obtained by ELISAs and bioassays. These data emphasize the necessity of establishing international stand ards for cytokine assays in order to render the interpretation of biol ogical and medical data more reliable.