Optimal cut-off values for tumor markers in cerebrospinal fluid with ROC curve analysis

To select optimal cut-off values of tumor markers in cerebrospinal fluid for the diagnosis of meningeal carcinomatosis, the concentrations of CEA, CA125, CA153, CA199, CA724, CYFRA21-1, AFP and NSE were determined by means of double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) in 21 MC patients, 25 cancer patients without leptomeningeal disease (group one) and 45 meningitis patients (group two) using the Roche E170 modular immunoassay analyzer. Optimal cut-off values were selected based on a receiver-operating characteristic curve. The results showed that CA125 and CEA in CSF were optimal diagnostic indices distinguishing between MC patients and cancer patients without leptomeningeal disease. Cut-off values for CA125 and CEA were 1.715 microliters and 0.274 microgram/l, respectively. In addition, CEA in CSF was the optimal diagnostic index distinguishing MC patients from meningitis patients. The cut-off value for CEA was 4.522 microgram/l.