Interlaboratory variability of urinary iodine measurements
-
Till Ittermann
,
Simone Johner
Abstract
Background:
The iodine status of populations is usually assessed by median urinary iodine concentrations (UIC) in population-based studies, but it is unclear to which extent UIC are comparable across different laboratories. The aim of our study was to investigate the variability of UIC measurements across three well-established German laboratories with long-term clinical-chemical expertise in iodine measurements and to compare these results to the gold standard inductively coupled plasma mass spectrometry (ICP-MS).
Methods:
UIC levels were measured from 303 urine samples derived from the “Dortmund Nutritional and Anthropometric Longitudinally Designed Study” and from volunteers of the University Medicine Greifswald at four different German laboratories. Three of these laboratories used Sandell-Kolthoff reaction with different digestion methods for UIC measurement (Lab1–Lab3), whereas one laboratory used ICP-MS as gold standard.
Results:
Median UIC levels were significantly different across the four laboratories (ICP-MS: 77 μg/L; Lab1: 69 μg/L; Lab2: 73 μg/L; Lab3: 111 μg/L). Linear regressions associating UIC levels of Lab1–Lab3 with UIC levels of ICP-MS showed intercepts significantly different from 0 and slopes significantly different from 1. Intraclass correlations (ICC) in comparison to ICP-MS were 0.91 for Lab1, 0.98 for Lab2, and 0.69 for Lab3. Using the digestion method of Lab2 in Lab3 improved the comparison of UIC levels of Lab3 with those from the ICP-MS (ICC=0.89).
Conclusions:
We have demonstrated larger interlaboratory variations across high-quality laboratories with long-lasting experience in iodine measurements indicating a relevant non-comparability of UIC measurements in iodine monitoring studies. Therefore, standardization of UIC measurements has to be expedited.
Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: This work was supported by EUthyroid. The project has received funding from the European Union’s Horizon 2020 Framework Programme, research and innovation program under grant agreement number 634453.
Employment or leadership: None declared.
Honorarium: None declared.
Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.
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Articles in the same Issue
- Frontmatter
- Editorial
- Analytical quality: an unfinished journey
- Reviews
- Update in diagnosis and management of primary aldosteronism
- Diagnosis biomarkers in acute intestinal ischemic injury: so close, yet so far
- Opinion Papers
- Irregular analytical errors in diagnostic testing – a novel concept
- A Black Swan in clinical laboratory practice: the analytical error due to interferences in immunoassay methods
- General Clinical Chemistry and Laboratory Medicine
- Reaching consensus on communication of critical laboratory results using a collective intelligence method
- Stability of routine biochemical analytes in whole blood and plasma/serum: focus on potassium stability from lithium heparin
- GFR estimation based on standardized creatinine and cystatin C: a European multicenter analysis in older adults
- Binding of bromocresol green and bromocresol purple to albumin in hemodialysis patients
- Interlaboratory variability of urinary iodine measurements
- The venous thromboembolic risk and the clot wave analysis: a useful relationship?
- Hematology and Coagulation
- Autovalidation and automation of the postanalytical phase of routine hematology and coagulation analyses in a university hospital laboratory
- Reference Values and Biological Variations
- Indirect method for validating transference of reference intervals
- Differences in levels of albumin, ALT, AST, γ-GT and creatinine in frail, moderately healthy and healthy elderly individuals
- Cancer Diagnostics
- Serum exosomal hnRNPH1 mRNA as a novel marker for hepatocellular carcinoma
- Intragenic hypomethylation of DNMT3A in patients with myelodysplastic syndrome
- Cardiovascular Diseases
- Evaluation of analytical performance of a new high-sensitivity immunoassay for cardiac troponin I
- MEF2C loss-of-function mutation associated with familial dilated cardiomyopathy
- Letter to the Editor
- Hyperuricemia does not seem to be an independent risk factor for coronary heart disease
- Reply to: Hyperuricemia does not seem to be an independent risk factor for coronary heart disease
- Preanalytics of ammonia: stability, transport and temperature of centrifugation
- Influence of delayed separation of plasma from whole blood on Cu, I, Mn, Se, and Zn plasma concentrations
- Copeptin as a diagnostic and prognostic biomarker in patients admitted to Emergency Department with syncope, presyncope and vertiginous syndrome
- Development of an internally controlled quantitative PCR to measure total cell-associated HIV-1 DNA in blood
- Selective changes in cholesterol metabolite levels in plasma of breast cancer patients after tumor removal
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