Rapid determination of serum testosterone by liquid chromatography-isotope dilution tandem mass spectrometry and a split sample comparison with three automated immunoassays.

OBJECTIVES: To develop a rapid convenient-to-implement high performance liquid chromatography-isotope dilution tandem mass spectrometry (LC-IDMS/MS) method for determination of serum testosterone concentration in routine clinical laboratories. METHODS: Following extraction by organic solvents, an Agilent 1200 Series HPLC system coupled to an API 5000 mass spectrometer equipped with an atmospheric pressure chemical ionization ion source was used to separate, detect and quantify serum testosterone. Ion-transitions of m/z 289.2-->109.1 and 294.2-->113.2 were used to monitor testosterone and testosterone-2,2,4,6,6-d(5), respectively. RESULTS: Functional sensitivity was 0.056 nmol/L (CV 20%). Within-run and total imprecision were 4.6% and 5.2% at 1.3 nmol/L, 2.4% and 4.3% at 11.0 nmol/L, and 1.9% and 1.9% at 23.4 nmol/L respectively. The LC-MS/MS method agreed closely with three automated immunoassays when the concentration of testosterone exceeded 3 nmol/L. However, the immunoassays showed a positive bias at concentrations below 3 nmol/L. CONCLUSION: This method provides a rapid, simple, highly selective and sensitive procedure that can be easily used for determination of serum testosterone in routine clinical laboratories. It measures serum testosterone precisely and accurately at concentrations found in children and adults of both genders.