Optimal collection of blood samples for the measurement of tumor necrosis factor α

Abstract

We have examined how delayed separation of plasma from cells affects the recovery of recombinant human tumor necrosis factor α (rhTNFα) from whole blood. Storage of heparinized whole blood samples at room temperature for 1 hr results in a significant (p = 0.036) fall in recovery of plasma TNFα from 788 ± 119 pg/mL to 472 ± 77 pg/mL, measured by specific enzyme-linked immunosorbent assay (ELISA). Storage of whole blood samples at 4°C for 1 hr reduces but does not prevent the fall in recovery of plasma TNFα: 725 ± 82 pg/mL at time 0, 472 ± 81 pg/mL after 1 hr, p = 0.038. Recovery of bioactive TNFα (cytotoxocity for L929 cells) after 1 hr at room temperature is also significantly reduced from 576 ± 139 pg/mL to 450 ± 154 pg/mL, p = 0.036. Studies with 125I-rhTNFα confirmed the fall in plasma activity and revealed a rapid commensurate increase in 125I-rhTNFα activity in the cell fractions. We recommend that clinical samples for the measurement of cytokines should be kept at 4°C and separated rapidly (within half an hour) before storing the plasma at −70°C.