Background: The measurement of alpha-fetoprotein (AFP) in cerebrospinal fluid (CSF) is important for the diagnosis of intracranial or intraspinal trophoblastic tumors. The current study was performed to establish reference values for AFP in CSF and to explore the relationship of CSF AFP and serum AFP in patients.
Material and methods: CSF samples were obtained from 351 inpatients admitted because of various neurological diseases, excluding those who were pregnant, had active liver disease, or who had trophoblastic or other malignant tumors. In 256 of the 351 patients, paired samples of CSF and serum were obtained. Both CSF AFP and serum AFP were measured. The 97.5th percentile and maximum value of CSF AFP were obtained. The CSF AFP and serum AFP concentrations in each of the 256 paired samples were compared.
Results: The 97.5th percentile and maximum value of CSF AFP concentration for overall participants were 1.042 and 1.950 g/L, respectively. The CSF AFP concentration was found to be higher than the simultaneous serum AFP concentration only in 1.6% (4/256) of participants.
Conclusions: The reference value determined in this study for CSF AFP is significantly lower than that usually used in clinical practice. A CSF AFP concentration higher than the simultaneous serum AFP concentration but lower than the upper reference limit does not necessarily suggest abnormal intrathecal AFP-secretion.