title: Relationship between Serum Testosterone and Fracture Risk in Men: A Comparison of RIA and LC-MS/MS.
abstract: BACKGROUND
  Serum testosterone can be measured by LC-MS/MS and RIA. We investigated whether the testosterone-fracture relationship was affected by the method of measurement.
  
  
  METHODS
  We measured total testosterone (TT) by LC-MS/MS (TTLC-MS/MS) and RIA (TTRIA) in serum samples collected from 602 men whose incident fractures had been continuously ascertained by x-ray reports from 1989 to 2010. We measured bone mineral density (BMD) by dual-energy x-ray absorptiometry. The association between TT and fracture risk was assessed by the Cox proportional hazards model, taking into account the effect of age and BMD.
  
  
  RESULTS
  Mean TTLC-MS/MS was higher than TTRIA by 27 ng/dL (95% CI 13-41). The concordance correlation coefficient between TTLC-MS/MS and TTRIA was 0.72 (95% CI 0.68-0.76). The Deming regression equation linking the 2 measurements was ln(TTLC-MS/MS + 10) = 0.87 + 0.87 × ln(TTRIA + 10). The hazard ratio of fracture per SD decrease in TT was 1.32 (95% CI 1.12-1.54) for TTLC-MS/MS and 1.23 (1.06-1.43) for TTRIA. The correlation between predicted probabilities of fracture by TTLC-MS/MS and TTRIA was r = 0.96, with the mean difference being 0.01% (95% CI -6.1% to 6.2%). Slightly more patients were classified as having hypogonadism if TTRIA was used (29% vs 26%).
  
  
  CONCLUSIONS
  The concordance between LC-MS/MS and RIA in the measurement of serum TT was moderate. Moreover, the magnitude of association between testosterone and fracture risk in older men was largely unaffected by the method of measurement.
authors.affiliation: Osteoporosis and Bone Biology Program and.
authors.forename: Thach S
authors.initials: TS
authors.lastname: Tran
authors.affiliation: Osteoporosis and Bone Biology Program and Clinical School, St. Vincent's Hospital, Sydney, Australia;
authors.forename: Jacqueline R
authors.initials: JR
authors.lastname: Center
authors.affiliation: Bone Research Program, ANZAC Research Institute, The University of Sydney, Sydney, Australia;
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Seibel
authors.affiliation: Osteoporosis and Bone Biology Program and Clinical School, St. Vincent's Hospital, Sydney, Australia; Clinical Translation and Advanced Education, Garvan Institute of Medical Research, Sydney, Australia; School of Medicine, Sydney, University of Notre Dame Australia, Sydney, Australia;
authors.forename: John A
authors.initials: JA
authors.lastname: Eisman
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology and Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT;
authors.forename: Mark M
authors.initials: MM
authors.lastname: Kushnir
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology and Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT;
authors.forename: Alan L
authors.initials: AL
authors.lastname: Rockwood
authors.affiliation: Osteoporosis and Bone Biology Program and School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia; Centre for Health Technologies, University of Technology, Sydney, Australia. t.nguyen@garvan.org.au.
authors.forename: Tuan V
authors.initials: TV
authors.lastname: Nguyen
mesh_terms: D000368:Aged; D015519:Bone Density; D002853:Chromatography, Liquid; D050723:Fractures, Bone / Q000097:blood* / Q000453:epidemiology*; D006801:Humans; D008297:Male; D016016:Proportional Hazards Models; D012307:Risk Factors; D053719:Tandem Mass Spectrometry; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone