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Interlaboratory variability of urinary iodine measurements
Till Ittermann1, Simone Johner2, Harald Below3
1Institute for Community Medicine, University Medicine Greifswald, Greifswald, Germany.
Clinical Chemistry and Laboratory Medicine
|September 24, 2017
Summary
Urinary iodine concentration (UIC) measurements vary significantly between high-quality labs, impacting population iodine status assessments. Standardization is urgently needed to ensure accurate iodine monitoring.
Area of Science:
- Clinical Chemistry
- Nutritional Science
- Analytical Chemistry
Background:
- Population iodine status is typically assessed using median urinary iodine concentrations (UIC).
- Comparability of UIC measurements across different laboratories remains unclear.
- This study addresses variability in UIC measurements among experienced German laboratories.
Purpose of the Study:
- To investigate interlaboratory variability of urinary iodine concentration (UIC) measurements.
- To compare UIC results from three established laboratories using the Sandell-Kolthoff reaction against the gold standard, inductively coupled plasma mass spectrometry (ICP-MS).
Main Methods:
- Analyzed 303 urine samples from two German cohorts.
- Measured UIC using the Sandell-Kolthoff reaction at three laboratories (Lab1-Lab3).
- Compared results to ICP-MS measurements from a fourth laboratory (gold standard).
Main Results:
- Significant differences in median UIC levels were observed across the four laboratories.
- Linear regressions showed significant deviations from the gold standard (intercepts ≠ 0, slopes ≠ 1).
- Intraclass correlations (ICC) with ICP-MS ranged from 0.69 (Lab3) to 0.98 (Lab2), indicating substantial variability.
Conclusions:
- High interlaboratory variation exists even among experienced laboratories, compromising UIC measurement comparability.
- Current UIC measurements in iodine monitoring studies may not be directly comparable.
- Expedited standardization of UIC measurement methods is crucial for reliable iodine status assessment.
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