Urinary 99m-Tc-diphosphonate excretion as a simple method to quantify bone metabolism

Abstract

Twenty-four-hour whole-body retention (WBR) of 99m-Tc-methylene-diphosphonate (an index of bone turnover) was determined by whole-body counting (WBR_s) and complementarily by urine counting (WBR_u) in nineteen subjects with normal to highly increased bone turnover. WBR_s and WBR_u correlated well (r = 0.94, P<0.001), and gave almost the same results. Both WBRs correlated equally well with serum alkaline phosphatase and urine hydroxyproline/creatinine (r = 0.82-0.93). Coefficient of variation in WBR_u was 7.0%, determined by duplicate measurements in sixteen normals. The injected dose of diphosphonate did not influence WBR_u. However, since almost 50% of the diphosphonate excreted in urine appeared during the first few hours after the i. v. injection, the method of WBR_u requires careful urine collection. Thus, the simple WBR_u determination provides the same information on bone metabolism as does the more cumbersome and expensive WBR_s technique.

Key Words:

• alkaline phosphatase
• bone-seeking radionuclides
• bone turnover
• diphosphonates
• hydroxyproline