The early fall in levels of S-100 beta in traumatic brain injury

Protein S-100 beta has been suggested as a prognostic marker in traumatic brain injury. However, little is known of its behaviour in the immediate post-injury period. With Ethics Committee approval, we recruited 30 patients with a history of head injury presenting to our Accident and Emergency Department. Blood was taken on arrival and at four hours post-injury. Serum S-100 beta was estimated using an immunoluminometric assay. Levels of S-100 beta were seen to fall rapidly with time. Half-time was distributed non-parametrically with a median of 198 minutes. Using the Mann-Whitney U test we found a statistically significant difference between non-desirable (Glasgow Outcome Score 1-3) and desirable (Glasgow Outcome Score 4-5) outcome on admission (p = 0.0155) but not at four hours (p = 0.1336). Levels of S-100 beta fell rapidly after its release following traumatic brain injury. Time after injury is therefore critical in assessing the significance of levels of S-100 beta, and sampling should be as early as possible to gain maximum information. If S-100 beta is to be assessed as a monitor of ongoing brain injury in the intensive therapy unit sampling must be frequent (e.g. every 4 hours) to be able to detect rises in serum levels before they have decayed to baseline.