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Clin Chem. 2005 Aug;51(8):1472-9. Epub 2005 Jun 16.

Testosterone measurement by isotope-dilution liquid chromatography-tandem mass spectrometry: validation of a method for routine clinical practice.

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1
SAS Centre for Steroid Hormones (Leeds), Department of Clinical Biochemistry and Immunology, Leeds General Infirmary, Leeds, United Kingdom. marion.cawood@leedsth.nhs.uk

Abstract

BACKGROUND:

Immunoassay is unsatisfactory for measuring the testosterone concentrations typically found in women. Bench-top tandem mass spectrometers are a viable alternative technology for measurements in the clinical laboratory.

METHODS:

We used stable-isotope dilution liquid chromatography-tandem mass spectrometry (ID/LC-MS/MS) to measure testosterone in plasma and serum. The sample volume was 50 muL in duplicate; preparation and analysis were carried out in a single tube, and a batch of 192 tubes was analyzed in 17.5 h.

RESULTS:

Intra- and interassay imprecision was <15% in the range 0.3-49 nmol/L. Recovery of testosterone added to samples at concentrations of 0.625-20 nmol/L was 96% (CV = 12%; n = 26). Six samples were serially diluted with double charcoal-stripped serum to demonstrate linearity. Correlation (r(2)) with isotope-dilution gas chromatography-mass spectrometry for 20 pools of clinical samples (range, 0.5-38.5 nmol/L) was 0.99. Correlations with our extraction RIA were 0.97 for clinical samples from men (range, 8-46.3 nmol/L) and 0.66 for samples from women (range, 0.7-3.0 nmol/L), but were 0.35 for male samples containing <3 nmol/L testosterone and 0.77 for female samples containing >8 nmol/L. Various steroids added to double charcoal-stripped serum showed no interference at the retention time of the testosterone peak.

CONCLUSIONS:

The ID/LC-MS/MS method has improved accuracy compared with immunoassay. The low sample volume and simplicity, rapidity, and robustness of the method make it suitable for use as a high-throughput assay in routine clinical biochemistry laboratories.

PMID:
15961553
DOI:
10.1373/clinchem.2004.044503
[Indexed for MEDLINE]
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