We investigated the level of S-100 protein in blood as an indicator of brain damage in 71 patients suffering from subarachnoid haemorrhage (SAH) due to ruptured aneurysms. Concentrations of S-100 protein were determined by micro-titre based immunofluorometic assay detecting predominantly S-100b on blood samples obtained 24 hours, 3 days and 7 days after onset of symptoms in patients with SAH and from 120 healthy control subjects. Neurological status was assessed using the Hunt and Hess (HH) scale on admission and by the Glasgow Outcome Scale (GOS) 6 months later. Mean concentrations of S-100 protein in blood were significantly (p < 0.0001) higher in patients 24 hours (0.263 +/- 0.387 microgram/l), 3 days (0.192 +/- 0.288 microgram/l) and 7 days (0.256 +/- 0.442 microgram/l) after onset of SAH symptoms compared to controls (0.050 +/- 0.081 microgram/l). More severe neurological symptoms (higher HH scale scores) on admission correlated with higher S-100 levels on admission (R = 0.70) and Day 3 (R = 0.66) (p < 0.0001). Worse outcome (lower GOS score) 6 months after SAH was also associated with higher plasma concentration of S-100 in the first week after SAH. In summary, this study showed that in patients with SAH due to ruptured aneurysm, S-100 protein levels correlate with early neurological deficit and are as sensitive as HH scores in predicting neurological outcome (GOS scores). Measurement of S-100 protein in blood is a reliable non-invasive method and may be clinically useful to screen for and monitor progression of central nervous system diseases of various origins.

Blood levels of S100B and GFAP indicate the severity of brain damage and are correlated with neurological prognosis after trauma. Both methods can yield additional prognostic information if combined with clinical and CCT findings.

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