[en] BACKGROUND: Cortisol measurement is useful in evaluation of Cushing syndrome, adrenal insufficiency, mineralocorticoid excess and congenital adrenal hyperplasia. We developed a liquid chromatography–tandem mass spectrometry (LCMS/MS) method for salivary and urinary cortisol and we determined the 95th percentile (p95) for the urinary and salivary cortisol. We compared them to the Mayo Clinic expected values.
METHODS: Saliva at 8 am and 11 pm and 24h urine were obtained from 32 healthy (22 female, 34.3±9.3 yo) volunteers. We performed validation with the enoval software (Arlenda, Belgium). For the validation, we used water or urine with spiked known amounts of cortisol for the CORS and CTU respectively. For the CORS, samples were centrifuged, deuterium labelled cortisol was added as internal standard and the protein precipated by acetonitril. The supernatant was evaporated, dissolved in methanol acidified with acetic acid and analyzed by LCMS/MS. For CTU, samples were centrifuged, deuterium labelled cortisol was added as internal standard and diluted by the ammonium acetate and analyzed by LCMS/MS. At the Mayo Clinic, the expected values were 1-7.5 μg/L (7 a.m-9 a.m) and <1 μg/L (11-12 p.m) for CORS and 3.5-45 μg/24h (<18yo) for CTU.
RESULTS: For the CTU, the with-in run did not exceed 3% (0.4-3%) and the between-run did not exceed 3.1% (0.4-3.1%) for 1.5-750 μg/L. The limit of quantification was 1.5 μg/L. The linearity was good between 1.5 and 750 μg/L. The recovery is 97.9±2.2% (95%CI for the mean: 92.4-101.1%). For the CORS, the with-in run and between run did not exceed 8% (1.9-8%) for 1.15-8.65 μg/L. The limit of quantification was 1.15 μg/L. The analyse presents a good linearity between 1.15 and 8.65 μg/L. The recovery is 99.9±2.9% (95%CI for the mean: 94.2-108.7%). The p95 for the CTU according to the CLSI C28-A3 was 33 μg/24h, and for the CORS was 5.42 μg/L at 8 am and 0.7 μg/L at 12 pm.
CONCLUSIONS: Our developed method in liquid chromatography tandem mass spectrometry was validated for the measurement of urinary and salivary cortisol. Our findings indicate that the proposed analytical methods were suitable for routine purposes and useful in many pathological conditions.The expected values confirm these defined by the Mayo Clinic.
Disciplines :
Laboratory medicine & medical technology
Author, co-author :
LE GOFF, Caroline ; Centre Hospitalier Universitaire de Liège - CHU > Chimie médicale
DELCOUR, Sandra ; Centre Hospitalier Universitaire de Liège - CHU > Laboratoire central
PEETERS, Stéphanie ; Centre Hospitalier Universitaire de Liège - CHU > Chimie médicale
CRINE, Yannick ; Centre Hospitalier Universitaire de Liège - CHU > Chimie médicale