A SPECIFIC AND SENSITIVE ELISA FOR MEASURING S-100B IN CEREBROSPINAL-FLUID

A sensitive, simple and specific sandwich ELISA for S-100b is describe d. This method involves the binding of a monoclonal anti-S-100b antibo dy to the wall of a microtitre plate. This capture antibody is subsequ ently incubated with S-100b standard, control or patient sample in the form of cerebrospinal fluid (CSF). After incubation, the microtitre p late is washed and horseradish peroxidase-labelled polyclonal anti-S-1 00b is added (detector antibody). The amount of detector antibody boun d to the microtitre plate is proportional to the amount of S-100b in t he sample. The assay has a lower limit of detection of 0.04 ng/ml and shows < 0.006% reactivity with the closely related polypeptide S-100a. The assay has a mean within-batch precision of 9.3 and 5.6% at S-100b concentrations of 0.38 and 0.8 ng/ml, respectively. The between batch precision is 8.9 and 8.1% at S-100b concentrations of 0.12 and 0.34 n g/ml, respectively. The recovery of S-100b from CSF spiked with 0.5 ng /ml was 94% with a CV of 8.5%. The assay may be completed in less than 5 h using precoated microtitre plates, thus lending itself to routine use in clinical laboratories. Using this ELISA, 154 CSF samples were analysed and 19% of samples were found to have elevated levels. The hi ghest levels were found in patients with cerebral haemorrhage or centr al nervous system malignancy. S-100b concentrations from individuals w ithout evidence of neurological disease were found to be less than 0.4 ng/ml. Only 5% of patients with multiple sclerosis were found to have elevated CSF S-100b concentrations. Serial CSF samples taken from a p atient with an infected in-dwelling shunt showed a dramatic decline, s uggesting that S-100b is rapidly cleared. (C) 1997 Elsevier Science B. V.