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A study to determine the dependence of 99mTc-MDP protein binding on plasma clearance and serum albumin concentration
Amelia E B Moore1, Glen M Blake, Ignac Fogelman
1King's College London School of Medicine, UK. amelia.moore@kcl.ac.uk
Background:
The measurement of protein binding is essential for accurate quantitative studies of skeletal kinetics using Tc-methylene diphosphonate (Tc-MDP). In this study, the dependence of Tc-MDP protein binding on total plasma clearance (Ktotal) and serum albumin concentration was investigated using data from two groups of patients.
Method:
The first group (study 1) consisted of 71 patients referred for a Tc-MDP bone scan examination. The second group (study 2) consisted of 100 subjects referred for a determination of glomerular filtration rate (GFR) and injected with 3 MBq Tc-MDP and 3 MBq Cr-EDTA. Free Tc-MDP was measured using ultrafiltration and the percentage of free Tc-MDP analysed for the effect of Ktotal and serum albumin concentration using multivariate regression analysis.
Results:
When the percentage of free Tc-MDP was analysed for the effect of Ktotal and serum albumin, highly significant relationships were found at the 2, 3 and 4 h time points. Subjects with higher values of Ktotal or serum albumin concentration had a lower percentage of free Tc-MDP and the magnitude of the regression coefficients increased with time.
Conclusion:
Multivariate regression analysis confirmed that Ktotal and serum albumin were highly significant factors in determining the percentage of free Tc-MDP measured at the 2, 3 and 4 h time points.
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