Determination of shelf life and activation energy for tumor necrosis factor-alpha in cerebrospinal fluid samples

The cytokine rumor necrosis factor-alpha (TNF-alpha) plays a prominent role in the inflammatory response and has been quantified in several kinds of body fluids. A safe method for keeping samples under the best storage conditions for later studies is clearly needed. We estimated TNF-alpha shelf life by using an accelerated stability testing protocol based on the Arrhenius equation. We investigated two kinds of samples: cerebrospinal fluid (CSF) normal pool (from patients without meningitis) and CSF pathological pool (from patients with pyogenic meningitis). Results of the stress protocol indicated that storing both normal and pathological CSF samples at -70 degrees C would maintain sample stability-i.e., retain at least 90% of the original TNF-alpha content-for approximately 5 years. At -20 degrees C and 4 degrees C, the projected stability time at which the same recovery would be obtained was 190 and 90 days, respectively.