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

Area of Science:

• Nuclear Medicine
• Biochemistry
• Bone Metabolism

Background:

• Assessing bone turnover is crucial for diagnosing and monitoring bone diseases.
• Traditional methods like whole-body counting (WBRs) for 24-hour technetium-99m-labeled methylene diphosphonate retention are effective but resource-intensive.

Purpose of the Study:

• To evaluate the accuracy and practicality of urine counting (WBRu) as an alternative to whole-body counting (WBRs) for determining 24-hour whole-body retention (WBR).
• To assess the correlation between WBRu and established biochemical markers of bone turnover.

Main Methods:

• Nineteen subjects with varying bone turnover rates underwent 24-hour whole-body retention (WBR) measurement using both whole-body counting (WBRs) and urine counting (WBRu).
• Correlation analyses were performed between WBRs, WBRu, serum alkaline phosphatase, and urine hydroxyproline/creatinine ratios.
• Reproducibility of WBRu was assessed via duplicate measurements in 16 normal subjects.

Main Results:

• A strong correlation (r = 0.94) was observed between WBRs and WBRu, indicating comparable results.
• Both WBR methods showed strong correlations with serum alkaline phosphatase and urine hydroxyproline/creatinine (r = 0.82-0.93).
• Urine counting (WBRu) demonstrated a coefficient of variation of 7.0% and was not influenced by the injected diphosphonate dose, though careful urine collection is necessary due to rapid excretion.

Conclusions:

• Urine counting (WBRu) is a reliable and simpler alternative to whole-body counting (WBRs) for assessing 24-hour whole-body retention (WBR) of technetium-99m-labeled methylene diphosphonate.
• WBRu provides equivalent information on bone metabolism compared to the more complex WBRs technique.
• This finding supports the use of WBRu for routine clinical assessment of bone turnover, offering a cost-effective and less cumbersome approach.