title: Correlation between Serum Levels of 3,3',5'-Triiodothyronine and Thyroid Hormones Measured by Liquid Chromatography-Tandem Mass Spectrometry and Immunoassay.
abstract: OBJECTIVE
  For measuring serum 3,3',5'-triiodothyronine (rT3) levels, radioimmunoassay (RIA) has traditionally been used owing to the lack of other reliable methods; however, it has recently become difficult to perform. Meanwhile, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has recently been attracting attention as a novel alternative method in clinical chemistry. To the best of our knowledge, there are no studies to date comparing results of the quantification of human serum rT3 between LC-MS/MS and RIA. We therefore examined the feasibility of LC-MS/MS as a novel alternative method for measuring serum rT3, thyroxine (T4), and 3,5,3'-triiodothyronine (T3) levels.
  
  
  METHODS
  Assay validation was performed by LC-MS/MS using quality control samples of rT3, T4, and T3 at 4 various concentrations which were prepared from reference compounds. Serum samples of 50 outpatients in our department were quantified both by LC-MS/MS and conventional immunoassay for rT3, T4, and T3. Correlation coefficients between the 2 measurement methods were statistically analyzed respectively.
  
  
  RESULTS
  Matrix effects were not observed with our method. Intra-day and inter-day precisions were less than 10.8% and 9.6% for each analyte at each quality control level, respectively. Intra-day and inter-day accuracies were between 96.2% and 110%, and between 98.3% and 108.6%, respectively. The lower limit of quantification was 0.05 ng/mL. Strong correlations were observed between the 2 measurement methods (correlation coefficient, T4: 0.976, p < 0.001; T3: 0.912, p < 0.001; rT3: 0.928, p < 0.001).
  
  
  CONCLUSIONS
  Our LC-MS/MS system requires no manual cleanup operation, and the process after application of a sample is fully automated; furthermore, it was found to be highly sensitive, and superior in both precision and accuracy. The correlation between the 2 methods over a wide range of concentrations was strong. LC-MS/MS is therefore expected to become a useful tool for clinical diagnosis and research.
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sakai
authors.affiliation: Pharmacokinetics Research Department of ASKA Pharmaceutical Co., Ltd., Kawasaki, Kanagawa, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Nagao
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Sakurai
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Okumura
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Nagai
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Junpei
authors.initials: J
authors.lastname: Shikuma
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Rokuro
authors.initials: R
authors.lastname: Ito
authors.affiliation: Pharmacokinetics Research Department of ASKA Pharmaceutical Co., Ltd., Kawasaki, Kanagawa, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Imazu
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Miwa
authors.affiliation: Department of Diabetes, Endocrinology and Metabolism, Tokyo Medical University, Tokyo, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Odawara
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D002853:Chromatography, Liquid / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay / Q000379:methods*; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014285:Triiodothyronine, Reverse / Q000097:blood*
chemical_list: D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013974:Thyroxine