Neuronal acetylcholinesterase levels in cerebrospinal fluid and serum determined by a specific and sensitive immunoassay.

Acetylcholinesterase levels were determined in cerebrospinal fluid and serum of 272 patients with various neurological disorders. The patients were ordered in 13 diagnostic groups. The assay employed was an antigen capture assay based on an immobilized monoclonal antibody selective for neuronal acetylcholinesterase (Rasmussen et al., Clin. Chim. Acta 166 (1987) 17-25 (1)). In 100% of the cases the acetylcholinesterase levels in cerebrospinal fluid were 500-10,000 fold higher than expected for a regular serum-derived protein (0.1-0.5%) at the intact blood-brain barrier. In both compartments the test values showed wide variations, which were much greater in serum than in cerebrospinal fluid. No specific relationship was discernible between the values obtained and any of the diagnostic groups, although decreased levels of acetylcholinesterase were found in bacterial and viral meningitis, and elevated levels were found in groups with more chronic diseases. A possible transfer of acetylcholinesterase from cerebrospinal fluid to blood is discussed.