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Journal of Bone and Joint Surgery - British Volume, Vol 89-B, Issue 6,
736-741.
doi: 10.1302/0301-620X.89B6.18141 Copyright © 2007 by British Editorial Society of Bone and Joint Surgery The validity of serum levels as a surrogate measure of systemic exposure to metal ions in hip replacementJ. Daniel, FRCS, MS(Orth), Director of Research1; H. Ziaee, BSc(Hons), Biomedical Scientist1; P. B. Pynsent, PhD, Director2; and D. J. W. McMinn, FRCS, Consultant Orthopaedic Surgeon1
1 The McMinn Centre, 25 Highfield Road, Edgbaston, Birmingham B15 3DP, UK. Correspondence should be sent to Mr J. Daniel; e-mail: josephdaniel{at}mcminncentre.co.uk
Metal ions generated from joint replacements are a cause for concern. There is no consensus on the best surrogate measure of metal ion exposure. This study investigates whether serum and whole blood concentrations can be used interchangeably to report results of cobalt and chromium ion concentrations. Concentrations of serum and whole blood were analysed in 262 concurrent specimens using high resolution inductively-coupled plasma mass-spectrometry. The agreement was assessed with normalised scatterplots, mean difference and the Bland and Altman limits of agreement. The wide variability seen in the normalised scatterplots, in the Bland and Altman plots and the statistically significant mean differences between serum and whole blood concentrations suggest that they cannot be used interchangeably. A bias was demonstrated for both ions in the Bland-Altman plots. Regression analysis provided a possible conversion factor of 0.71 for cobalt and 0.48 for chromium. However, even when the correction factors were applied, the limits of agreement were greater than ±67% for cobalt and greater than ±85% for chromium, suggesting that serum and whole blood cannot be used interconvertibly. This suggests that serum metal concentrations are not useful as a surrogate measure of systemic metal ion exposure. This article has been cited by other articles:
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