Alpha-Fetoprotein (AFP), Spinal Fluid
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Alpha-fetoprotein (AFP) is an oncofetal glycoprotein, homologous with albumin that is produced both in early fetal life and in tumors arising from midline embryonic structures. AFP is synthesized in the yolk sac, liver, and gastrointestinal track of the fetus. In adults, the liver synthesizes AFP. AFP is not normally expressed in the central nervous system (CNS). AFP levels in liver are increased in hepatomas and hepatocellular and colon carcinomas, as well as in germ-cell tumors arising from the ovaries and nonseminomatous germ-cell tumors of the testes, testicular teratocarcinomas, and primary germ-cell tumors arising within the CNS. The presence of germinomas in the CNS and CNS involvement in metastatic cancer and meningeal carcinomatosis results in increased levels of AFP in cerebrospinal fluid.
An adjunct in the diagnosis of central nervous system (CNS) germinomas and meningeal carcinomatosis
Evaluating germ-cell tumors, including testicular cancer metastatic to the CNS in conjunction with beta-human chorionic gonadotropin measurement(1)
An adjunct in distinguishing between suprasellar dysgerminomas and craniopharyngiomas
A supplement to cerebrospinal fluid cytologic analysis
Alpha-fetoprotein (AFP) concentrations that exceed the upper end of normal are consistent with the presence of central nervous system germinoma, meningeal carcinomatosis, or metastatic nonseminomatous testicular cancer. AFP is not elevated in the presence of a craniopharyngioma.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Malignancy may occur without elevation of alpha-fetoprotein (AFP) concentration. AFP elevation occurs in approximately 70% of central nervous system germinomas. Measurement of beta-human chorionic gonadotropin is recommended to improve sensitivity of detection.
Values obtained with different assay methods or kits may be different and cannot be used interchangeably.
Test results cannot be interpreted as absolute evidence for the presence or absence of malignant disease.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Values for alpha-fetoprotein in cerebrospinal fluid have not been formally established for newborns and infants. The available literature indicates that by 2 months of age, levels comparable to adults should be reached.(Ann Clin Biochem 2005;42:24-29)
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Jubran RF, Finlay J: Central nervous system germ cell tumors: controversies in diagnosis and treatment. Oncology 2005;19:705-711
2. Seregni E, Massimino M, Nerini Molteni S, et al: Serum and cerebrospinal fluid human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) in intracranial germ cell tumors. Int J Biol Markers 2002;17(2):112-118
3. Coakley J, Kellie SJ: Interpretation of alpha-fetoprotein concentrations in cerebrospinal fluid of infants. Ann Clin Biochem 2005;42:24-29