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Variability in XRF-measured tibia lead levels.
A C Todd1, S Carroll, J H Godbold
1The Mount Sinai School of Medicine, Department of Community and Preventive Medicine, New York, NY 10029, USA. andrew.todd@mssm.edu
Physics in Medicine and Biology
|December 29, 2000
Summary
K-shell x-ray fluorescence (KXRF) measurements for bone lead may underestimate variability. Replicate measurements in cadavers and volunteers show individual uncertainty is lower than actual standard deviation, indicating a potential system deficiency.
Area of Science:
- Biomedical Engineering
- Environmental Health
- Analytical Chemistry
Background:
- Bone lead measurements are crucial for assessing cumulative lead exposure.
- 109Cd-based K-shell x-ray fluorescence (KXRF) is a common method for in vivo bone lead quantification.
- Previous studies suggest potential underestimation of measurement variability in KXRF.
Purpose of the Study:
- To assess the variability of 109Cd-based KXRF tibia lead measurements.
- To investigate factors influencing the standard deviation of replicate measurements.
- To determine if individual measurement uncertainty underestimates true variability.
Main Methods:
- Replicate KXRF measurements were performed on ten intact cadaver legs and nine dissected tibiae.
- In vivo measurements were conducted monthly for one year on four volunteers.
- Factors affecting the standard deviation of replicate measurements were analyzed.
Main Results:
- Average tibia lead levels ranged from 6-50 µg Pb/g bone mineral in cadavers and 6-13 µg Pb/g bone mineral in volunteers.
- Both cadaver and in vivo data confirmed that individual measurement uncertainty is an underestimate of the standard deviation of replicate measurements.
- This suggests a methodological deficiency common to most current 109Cd-based KXRF lead measurement systems.
Conclusions:
- The uncertainty associated with individual KXRF bone lead measurements does not fully capture the total variability.
- A methodological deficiency likely exists in current 109Cd-based KXRF systems, impacting accurate variability assessment.
- Further improvements in KXRF methodology are needed for more reliable bone lead quantification.