April - June 2006, Volume 2, Issue 2

Purice M, Gheorghiu ML, Caragheorgheopol A, Tanasescu R

Comparison between immunometric methods for the determination of FSH, LH, TSH and PRL hormones in CSF

Acta Endo (Buc) 2006, 2 (2): 151-161
doi: 10.4183/aeb.2006.151

Introduction: The necessity to determine the levels of pituitary hormones in the cerebrospinal fluid is motivated both by difficulties in the diagnosis of different neuroendocrine disorders, as well as by research purposes such as understanding the transport mechanisms of hormones through the blood brain barrier.\r\nObjective: The aim of this study was to compare the results obtained with different immunometric methods for some pituitary hormones in the serum and CSF in patients with neuroendocrine tumors.\r\nMaterials and methods: The levels of LH, FSH, PRL and TSH were determined simultaneously in the serum and CSF with 3 different immunometric methods using commercial kits: IRMA, FIA and Chemiluminescence for 36 patients. The validation of IRMA method on CSF samples was performed using the dilution test.\r\nResults: The dilution test - as one of validation criteria of an immunoassay - proved that the results obtained in the CSF using the commercially available kits were correct. This enables the use of this sensitive method to accurately demonstrate abnormal levels of pituitary hormones beyond the blood-brain barrier. The correlation between IRMA and FIA: Hormonal concentrations values obtained by IRMA correlate well with those measured by FIA for serum with no significant differences of the mean concentration value for FSH (r=0.93, p: NS) and LH (r=0.99, p: NS), but with a significant difference for PRL (r=0.88, p=0.002). In CSF, mean concentrations values correlate well and we found no differences for TSH (r =0.97, p: NS) and LH (r = 0.94, p: NS), but significant differences for PRL (r= 0.98, p=0.001) and FSH (r=0.98, p=0.001). Statistically significant differences were also found for the CSF/serum ratio for PRL (p=0.08), FSH (p=0.001) and LH (p=0.001). The ratios CSF/serum are significantly higher with IRMA method than with FIA for all the hormones. Except for one patient for all the others we found the ratio CSF/serum less than 1 showing that the pathologic significance of this parameter is not modified due to the type of immunometric assay. A statistically significant difference (p<0.001) was found for mean FSH concentration in CSF with FIA and Chemiluminescent assays .\r\nConclusions: Any immunometric method currently used for the determination of hormones in the serum or plasma has to be validated accordingly in order to be used on CSF. For obtaining results that can be interpreted and compared it is preferred that the same immunometric method is used on both serum and CSF, inside one group of patients. The presence of a control group for the results determined with that method is strongly recommended.

Keywords: immunometric methods, IRMA, FIA, Chemiluminescence, cerebrospinal fluid, pituitary hormones

Correspondence: Mariana Purice, Institute of Endocrinology, 36 Bd.Aviatorilor, 011863, Bucharest, Romania, email: mpurice_endo@yahoo.co.uk