title: Glucosephosphate isomerase as a CSF marker for leptomeningeal metastasis.
abstract: Glucosephosphate isomerase (GPI), also known as phosphohexoisomerase, is a glycolytic enzyme whose activity is elevated in serum and CSF of patients with primary and metastatic CNS tumors. To improve the diagnostic accuracy of leptomeningeal metastasis (LM), we measured GPI levels in CSF of 66 patients with CNS or systemic malignancies with suspected LM. We determined GPI kinetically using a coupled enzyme reaction assay. There were 31 males and 35 females, aged 1 to seventy-six. Thirty-one had primary brain tumors, and 35 had systemic cancer with suspected CNS metastasis. We analyzed 95 samples; GPI values ranged from 0.85 to 329.0 U/l (normal, less than 20 U/l). Compared with positive CSF cytology and myelography, GPI sensitivity was 53.5% and specificity 92.1% for the group as a whole. There was a highly significant association between elevated CSF GPI (greater than 20 U/l) and LM. The results were similar for both primary CNS and systemic malignancies. Although not very sensitive, an elevated CSF GPI strongly suggests LM and may aid in early diagnosis of this serious complication of cancer.
authors.affiliation: Department of Neurology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
authors.forename: H B
authors.initials: HB
authors.lastname: Newton
authors.forename: M
authors.initials: M
authors.lastname: Fleisher
authors.forename: M K
authors.initials: MK
authors.lastname: Schwartz
authors.forename: M G
authors.initials: MG
authors.lastname: Malkin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002556:Cerebrospinal Fluid Proteins / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D005188:False Negative Reactions; D005260:Female; D005956:Glucose-6-Phosphate Isomerase / Q000134:cerebrospinal fluid*; D006801:Humans; D007223:Infant; D007958:Leukocyte Count; D008297:Male; D008577:Meningeal Neoplasms / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000556:secondary*; D008875:Middle Aged
chemical_list: D002556:Cerebrospinal Fluid Proteins; D005956:Glucose-6-Phosphate Isomerase