The
desmosterol test for the diagnosis of central nervous system (CNS)
tumors is proposed in a simplified form. The procedure is based upon the analysis of
sterol profile in cerebrospinal fluid (CSF) by selected ion monitoring (SIM) technique. Applied to 55 patients with tumoral and non tumoral
CNS disease, the new test detects average levels of CSF
desmosterol in
tumor bearing patients that are tenfold higher than in the absence of CNS
neoplasia. On an individual basis, a concentration of CSF
desmosterol equal to or higher than the mean plus twice the standard deviation for the reference group of patients with no CNS
tumor, is considered a positive result. Based on this criterion, a correct diagnosis was made in 73% of cases vs 77% of the former test, which required a 5-day treatment period with a
desmosterol-
reductase inhibitor in order to increase CSF
desmosterol concentration. With this revised procedure CSF
desmosterol can be detected in smaller volumes of CSF without any
drug pretreatment, thus making the test more suitable for clinical application.