Abstract
BackgroundSkeletal uptake of 99mTc labelled methylene diphosphonate (99mTc-MDP) is used for producing images of pathological bone uptake due to its incorporation to the sites of active bone turnover. This study was done to validate bone turnover markers using total skeletal uptake (TSU) of 99mTc-MDP.Methods22 postmenopausal women (52–80 years) volunteered to participate. Scintigraphy was performed by injecting 520 MBq of 99mTc-MDP and taking whole body images after 3 minutes, and 5 hours. TSU was calculated from these two images by taking into account the urinary loss and soft tissue uptake. Bone turnover markers used were bone specific alkaline phosphatase (S-Bone ALP), three different assays for serum osteocalcin (OC), tartrate resistant acid phosphatase 5b (S-TRACP5b), serum C-terminal cross-linked telopeptides of type I collagen (S-CTX-I) and three assays for urinary osteocalcin (U-OC).ResultsThe median TSU of 99mTc-MDP was 23% of the administered activity. All bone turnover markers were significantly correlated with TSU with r-values from 0.52 (p = 0.013) to 0.90 (p < 0.001). The two resorption markers had numerically higher correlations (S-TRACP5b r = 0.90, S-CTX-I r = 0.80) than the formation markers (S-Total OC r = 0.72, S-Bone ALP r = 0.66), but the difference was not statistically significant. TSU did not correlate with age, weight, body mass index or bone mineral density.ConclusionIn conclusion, bone turnover markers are strongly correlated with total skeletal uptake of 99mTc-MDP. There were no significant differences in correlations for bone formation and resorption markers. This should be due to the coupling between formation and resorption.
Highlights
Skeletal uptake of 99mTc labelled methylene diphosphonate (99mTc-MDP) is used for producing images of pathological bone uptake due to its incorporation to the sites of active bone turnover
We aimed to investigate if uptake of 99mTc-MDP is more related to bone formation or resorption, assuming that if any of the bone formation markers had a significantly greater correlation with total skeletal uptake (TSU), over the others; it could have been regarded as a relatively specific measure of bone formation
Bone mineral density Areal bone mineral density (BMD) of total body, lumbar spine, femoral neck and bone mineral content (BMC) of the total body were measured by dual-energy x-ray absorptiometry (DXA) (Lunar DPX-L® Madison, USA)
Summary
Skeletal uptake of 99mTc labelled methylene diphosphonate (99mTc-MDP) is used for producing images of pathological bone uptake due to its incorporation to the sites of active bone turnover. Technetium-99m (99mTc) labelled diphosphonates are commonly used in scintigraphic uptake studies to detect lesions in conditions such as cancer metastasis, occult fractures and osteomyelitis due to their high affinity to metabolically active sites in bone. In these procedures the skeletal or extra-osseous accumulation of 99mTc labelled methylene diphosphonate (99mTcMDP) is used to identify the lesions as "hot spots" [10,11]. In earlier studies the measurement of 24-hour whole body retention of 99mTc-MDP was used to assess the skeletal metabolism [12,13], before introducing the regional quantification of 99mTc-MDP activity by D'Addabbo et al [14] and Brenner et al [15]. To the best of our knowledge, the correlation between bone metabolism assessed by skeletal uptake of 99mTc-MDP and by bone turnover markers has been evaluated only in a few studies [13,16,17,18]
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