Determination of aldosterone in serum by liquid chromatography-tandem mass spectrometry.
Measurement of serum aldosterone is clinically important in the diagnosis of hypertension. While isotope dilution gas chromatography-mass spectrometry (ID-GC-MS) provides reliable results, it requires derivatization and is lengthy and time-consuming. Detection by liquid chromatography-mass spectrometry (LC-MS) is a potentially superior method. The analysis utilizes 0.5mL of serum. The samples were extracted with dichloromethane-ether. The extract was evaporated to dryness and aldosterone was analyzed by LC-MS/MS operating in the negative mode ESI after separation on a reversed-phase column. Aldosterone was also measured by RIA. The calibration curves for analysis of serum aldosterone exhibited consistent linearity and reproducibility in the range of 60-3000pmol/L. Interassay CVs were 4.3-7.5% at aldosterone concentrations of 97-993pmol/L. The lower limit of quantitation (LOQ) was 30pmol/L (signal to noise ratio=10). The mean recovery of the analyte added to serum ranged from 95 to 102%. The regression equation by LC-MS/MS (x) and RIA (y) method was: y=1.33x+185 (r=0.95; n=124). Sensitivity and specificity of the LC-MS/MS method for serum aldosterone offer advantages over GC-MS by eliminating derivatization. The novel method is rapid, reliable and simple to perform with a routine LC-MS/MS spectrometer. The sensitivity is adequate for patient samples. Aldosterone concentrations reported by nonextraction RIA were consistently higher than those produced by LC-MS/MS.
HUSLAB, Laboratory of Women's Clinic, P.O. Box 140, 00029 HUS, Helsinki, Finland. ursula.turpeinen@hus.fi
Ursula
U
Turpeinen
Esa
E
Hämäläinen
Ulf-Håkan
UH
Stenman
D000450:Aldosterone / Q000097:blood*; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D011863:Radioimmunoassay; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*
D000450:Aldosterone