[Enzyme immunoassay stability of alpha tumor necrosis factor in plasma and serum]

With an enzyme immunoassay (ELISA) the stability of tumor necrosis factor alpha (TNF-alpha) has been determined in serum and plasma with and without addition of a protease inhibitor (Aprotinin, Trasylol) 24 hours, as well as seven days after blood collection. It has been observed, that after blood collection the concentration of TNF-alpha decreases first and increases again six hours, (+4 degrees C) respectively twelve hours (-20 degrees C) later. Reasons for that might be: The active form of TNF-alpha is a trimer, the presence of TNF-binding proteins, the presence of TNF-antibodies. Furthermore it has been found, that TNF-alpha has the highest stability in plasma at -20 degrees C and -70 degrees C. The addition of Aprotinin had no significant influence on the stability.