Research article

Bone turnover markers are correlated with total skeletal uptake of ^99mTc-methylene diphosphonate (^99mTc-MDP)

Janaka Lenora¹ , Kristina Norrgren² , Ola Thorsson² , Per Wollmer² , Karl J Obrant¹ and Kaisa K Ivaska¹

¹Department of Orthopaedics, Malmö University Hospital, Lund University, SE 20502 Malmö, Sweden

²Department of Clinical Physiology, Malmö University Hospital, Lund University, SE 20502 Malmö, Sweden

author email corresponding author email

BMC Medical Physics 2009, 9:3doi:10.1186/1756-6649-9-3

Published:	30 March 2009

Abstract

Background

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. This study was done to validate bone turnover markers using total skeletal uptake (TSU) of ^99mTc-MDP.

Methods

22 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).

Results

The 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.

Conclusion

In 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.