Thach S Tran1, Jacqueline R Center2, Markus J Seibel3, John A Eisman4, Mark M Kushnir5, Alan L Rockwood5, Tuan V Nguyen6. 1. Osteoporosis and Bone Biology Program and. 2. Osteoporosis and Bone Biology Program and Clinical School, St. Vincent's Hospital, Sydney, Australia; 3. Bone Research Program, ANZAC Research Institute, The University of Sydney, Sydney, Australia; 4. 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; 5. ARUP Institute for Clinical and Experimental Pathology and Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT; 6. 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.
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.
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.