Method Validation of Human Chorionic Gonadotropin and α-Fetoprotein in Cerebrospinal Fluid: Aiding the Diagnosis of Intracranial Germ Cell Tumors.

ABSTRACT

BACKGROUND: Our study objective was to validate 2 individual methods to measure α-fetoprotein (AFP) and human chorionic gonadotropin (hCG) in cerebrospinal fluid (CSF) on the Roche cobas® 6000 analyzer. A 3-year retrospective chart review of CSF samples analyzed for AFP and hCG was also conducted. METHODS: Serum samples with high concentrations of AFP or hCG were added to aliquots of pooled CSF. Precision, linearity, detection limit, recovery, carryover, stability, and interference studies of the AFP and hCG+ß assays were performed. RESULTS: Within-day and day-to-day assay imprecision for AFP and hCG assays were <5% at all concentrations tested. The linear range of the AFP assay was established as 1.0-1100 µg/L, and limit of quantification (LOQ) was <1.0 µg/L. The linear range of the hCG assay was established as 1.0-9500 IU/L and LOQ 0.7 IU/L. There was no demonstrable matrix effect, and neither assay was affected by the presence of hemolysis or xanthochromia. AFP in CSF was stable at room and refrigerated temperatures for up to 48 h at concentrations of 19 and 306 µg/L but increased by 24 h at a concentration of 908 µg/L. AFP in CSF was stable frozen (-20 °C) for up to 7 days. hCG in CSF at all concentrations tested was stable at room, refrigerated, and frozen temperatures for up to 7 days. CONCLUSIONS: The Roche cobas 6000 AFP and hCG+ß assays accurately quantify AFP and hCG in CSF, facilitating rapid and accurate diagnosis as well as monitoring of intracranial germ cell tumors.