Measurement of S-100 protein in human blood and cerebrospinal fluid: analytical method and preliminary clinical results.

An immunofluorometric sandwich assay for determination of S-100 protein in cerebrospinal fluid (CSF) and blood is described. The lower detection limit was 0.015 micrograms/l of S-100 protein. Intra-assay and inter-assay imprecision (coefficients of variation, CVs) were 2.1 to 3.2% and 7.8 to 11.6%, respectively. S-100 protein recovery in cerebrospinal fluid was 94 to 103%. In blood the recovery varied from 67 to 96%, depending on blood samples used and the concentration of S-100 protein. The best recovery in blood was found using heparinized plasma. In healthy subjects 0.098 +/- 0.11 micrograms/l (mean +/- SD) of S-100 protein was detected (n = 30). In the CSF of otherwise healthy patients undergoing a myelography for lumbar pain 1.43 +/- 0.49 micrograms/l (mean +/- SD) of S-100 protein was found. Preliminary results from longitudinal studies on S-100 protein in neurosurgical patients indicate a positive correlation between S-100 protein blood levels and clinical course. Thus, the determination of S-100 protein in blood appears to be helpful in the monitoring of patients with neuronal damage.