Validation of the human chorionic gonadotropin immunoassay in cerebrospinal fluid for the diagnostic work-up of neurohypophyseal germinomas

Abstract

Background: The measurement of human chorionic gonadotropin (hCG) in cerebrospinal fluid (CSF) is useful for the differential diagnosis of suprasellar lesions. However, the concentrations that prove diagnostic for neurohypophyseal germinoma have not been well defined. In addition, the immunoassays used for such measurements are the same as those applied in serum, and few studies have been performed regarding the validation of such techniques in CSF. The present study aims to apply the Elecsysw hCG þ b immunoassay from Roche Diagnostics to measure hCG in CSF, as a useful tool in the diagnosis of neurohypophyseal germinomas in children and young adults. Methods: Validation of the immunoassay involved calculation of the functional sensitivity and reference values for hCG in CSF in 35 controls in the absence of pregnancy, trophoblastic disease or tumour pathology. For the clinical application study, three patients diagnosed with neurohypophyseal germinoma have been reviewed. Results: The functional sensitivity obtained was 0.4 IU/L. The reference values for hCG in CSF ranged from undetectable values to 0.7 IU/L. The hCG concentrations in CSF in the three studied patients, with confirmed diagnosis of neurohypophyseal germinoma, were 21.1, 32.6 and 23 IU/L, respectively. Conclusions: The Elecsysw hCG þ b immunoassay from Roche Diagnostics can be used to detect hCG in CSF with high precision. According to our results, CSF-hCG concentrations that exceed the established reference interval (undetectable values to 0.7 IU/L) in the presence of suprasellar lesions and hypophyseal stalk thickening must be considered pathological, establishing the need to exclude the presence of germinoma.