title: Sensitive quantitation of carcinoembryonic antigen in cerebrospinal fluid and its barrier-dependent differentiation.
abstract: Modification of an enzyme immunoassay using beads as solid phase allows the detection of 3 pg/ml carcinoembryonic antigen (CEA). The beads are shown to be advantageous for the extraction of proteins in highly diluted antigen solutions thus replacing a need for concentration of the sample. The mean concentration of CEA in pooled cerebrospinal fluid (CSF) from 120 control persons was shown to be 2.7 pg/ml. The mean of the CSF/serum concentration quotients of CEA was 0.0015 for normal blood CSF barrier function with a corresponding mean albumin CSF/serum quotient of 0.0048. From the ratio of these two quotients (QCEA/QA = 0.31) and the corresponding biological variation we constructed the normal range of an evaluation graph. In the range of a blood CSF barrier dysfunction, the discrimination line between values with or without a local CEA synthesis in brain was determined to be QCEA = 0.7 QA. Twenty-five out of 383 control persons and 29 out of 45 patients with a tumor metastasis had evaluable quotients. The evaluation graph had a high significance with respect to the identification of tumor metastasis: from a group of patients with a confirmed leptomeningeal metastasis 13 out of 13 and from a group of patients with intraparenchymatous tumor metastasis 10 out of 16 could be identified by CSF analysis. The CEA CSF/serum concentration quotient fits well in the concept of a molecular size-dependent filter function of the blood CSF barrier.
mesh_terms: D001812:Blood-Brain Barrier; D001932:Brain Neoplasms / Q000276:immunology / Q000556:secondary; D002272:Carcinoembryonic Antigen / Q000032:analysis / Q000134:cerebrospinal fluid*; D006801:Humans; D007124:Immunoenzyme Techniques; D009369:Neoplasms / Q000276:immunology; D012016:Reference Values
chemical_list: D002272:Carcinoembryonic Antigen