Have you caught that outlier yet? Evaluate the utility of repeat testing in nutritional and toxic element assessment

• Published in: Clinica chimica acta Vol. 528; pp. 84 - 89
• Main Authors: Smith, Eric A., Parker, Rebecca, Genesi, Bryce, Yang, Yifei K.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2022
• Subjects: Analytical reproducibility; Element analysis; Humans; ICP-MS; Laboratory operation efficiency; Mass Spectrometry - methods; Metals, Heavy; Reference Values; Spectrum Analysis; Trace Elements; QC; Cu; CV; TTE; Zn; Analytical reproducibility; Laboratory operation efficiency; MOM; ICP-MS; Element analysis; Co; Cr
• ISSN: 0009-8981; 1873-3492
• DOI: 10.1016/j.cca.2022.01.019

•ICP-MS and automation have improved analytical reproducibility of TTE assays.•Repeat analysis is required by regulatory agency to rule out analytical outliers.•This study evaluated the utility of repeat analysis for copper, zinc, chromium, and cobalt in serum or plasma.•The likelihood of detecting analytical outliers by repeat analysis is very low. Repeat testing is routinely required by regulatory bodies as a measure to rule out contamination in trace elements and heavy metal analysis, especially when the initial analysis result is outside the reference interval. However, its clinical utilities in detecting analytical measurement outliers have not been systematically evaluated in different clinical testing scenarios. In this study, we present an extensive evaluation of repeat testing and its comparison with the initial analysis in four serum and plasma trace element assays performed by inductively coupled plasma mass spectrometry. We demonstrate that the patient population distributions for these elements differ significantly from the reference interval established by healthy individuals. Accordingly, a significant proportion of the patient specimens would require repeat testing when using reference intervals as the threshold to perform repeat analysis. Crucially, comparison of the first analysis and repeat analysis reveals the limited utility of performing repeat measurements. The relative differences between the first and second measurements are consistent with the observed analytical imprecision of the assay and the likelihood of detecting actual analytical outliers is very low.