This is the first study to establish age-specific reference ranges for liquid chromatography-tandem mass spectrometry-measured TT and AD and calculated free T concentrations based on quantile regression analyses, accurately accounting for the observed low concentration range and the strong age dependency of these sex hormones in women.
Background: The accurate measurement of cortisol by immunoassay is compromised by the potential for cross-reactivity of reagent antibodies with structurally related steroids present in serum. This susceptibility is potentiated when normal steroid metabolism is altered pharmaceutically by antisteroidogenic drugs utilized in the management of Cushing's syndrome to moderate cortisol production. The clinical implications of falsely elevated cortisol results include over-treatment and unrecognized hypoadrenalism. To investigate the effect of the 11b-hydroxylase inhibitor metyrapone on serum cortisol assay, a comparison of measurement by immunoassay versus liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted. Methods: Cortisol was measured in serum from three patient groups: (1) patients receiving metyrapone (n ¼ 112 samples from 10 patients); (2) control group of patients diagnosed with Cushing's syndrome currently receiving no treatment (n ¼ 31); and (3) control group of patients with no adrenal pathology and not receiving medication known to interfere in cortisol immunoassay (n ¼ 67). Conclusions: These data show that liability of immunoassay measurement of serum cortisol to interference in patients receiving metyrapone may lead to erroneous clinical decisions concerning dose titration.
BACKGROUND:The recent interest of clinical laboratories in developing serum testosterone assays based on isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) stems from the lack of accuracy of direct immunoassays. In this study, we assessed the accuracy and state of standardization (traceability) of 4 published ID-LC-MS/MS procedures in a method comparison with an ID-gas chromatography (GC)-MS reference measurement procedure listed in the database of the Joint Committee for Traceability in Laboratory Medicine.
We have shown an excellent diagnostic sensitivity and specificity of LC-MS/MS SalC in the assessment of the HPA axis and superiority over SerC when CBG levels are altered. The exponential relationship between SerC and SalC supports the concept of CBG binding capacity saturation.
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