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Background: Given that both insufficient and excess maternal iodine have adverse consequences such as poor cognitive performance, delayed physical development and increased fetal and infant mortality, the determination of maternal iodine status is very important. In this study, we established and verified a method involving inductively coupled plasma-mass spectrometry (ICP-MS) technology for the rapid determination of the amniotic fluid iodine concentration (AFIC), breast milk iodine concentration (BMIC) and cerebrospinal fluid (CSF) iodine concentration (CSFIC)., Method: Amniotic fluid, breast milk and CSF were collected from residual samples at Peking Union Medical College Hospital (PUMCH). The linearity, detection limit, precision, recovery, carryover and matrix effect of the testing method using ICP-MS technology were thoroughly evaluated according to the EP-10-A2 evaluation protocol approved by the Clinical and Laboratory Standards Institute (CLSI) guidelines. Furthermore, we evaluated the AFIC, BMIC and CSFIC distributions among clinical patients from PUMCH., Results: The correlation coefficient (r) was higher than 0.99 (0.995-1.000). The limit of detection (LOD) was 0.233 µg/L, and the limit of quantification (LOQ) was 0.778 µg/L. For amniotic fluid, breast milk and CSF, the assay repeatabilities were 1.5%-1.8%, 1.9%-4.0% and 1.8%-4.0%, respectively, and the within-laboratory coefficient of variations (CV%) over five days were 3.3%-9.2%, 7.2%-8.0% and 3.2%-7.8%, respectively. The recovery rates ranged from 97.7% to 109.8%. Moreover, the median concentrations of iodine in the amniotic fluid, breast milk and CSF of the patients from PUMCH were 176.3 µg/L, 136.0 µg/L, and 81.8 µg/L, respectively., Conclusion: A rapid, stable and accurate method that incorporates ICP-MS technology for the determination of iodine concentration was established for amniotic fluid, breast milk and CSF in this study., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Rapid and simple method for serum and urine iodine is necessary for iodine-related diseases. This study aimed to establish and validate a simple and rapid method for quantification of iodine in human urine and serum using inductively coupled plasma mass spectrometry (ICP-MS). Generally, samples were diluted using water with 1.5% isopropanol and 7 mmol hydrous ammonium before analysis by the ICP-MS. Performance of the method was validated, and the urine and serum iodine levels of 72 pregnant women were analyzed. Results showed that the lower limit of detection of the ICP-MS method was 0.87 µg/L. No significant memory effects were observed. Recovery in both serum and urine was approximately 100%. Compared with NIST SRM3668, bias was <1%, exhibiting good accuracy. The inter-run coefficients of variation (CVs) for serum and urine iodine were 2.8-3.5% and 3.5-6.7%, respectively, and total CVs for serum and urine iodine were 3.2-3.7% and 3.9-6.7%, respectively. Comparison of the iodine results obtained by the ICP-MS method and the conventional S-K method revealed excellent correlation (r = 0.984, mean bias = -1.7%). The median urine iodine of pregnant women (125.5 μg/L) was lower than that of WHO criteria for iodine deficiency (median urinary iodine <150 μg/L) while 55.6% of the individuals with urine iodine level less than 150 μg/L. The median serum iodine level of the pregnant women was 69.0 μg/L. In conclusion, a rapid and simple ICP-MS method for urine and serum iodine measurements has been established and validated, and the pregnant women in Beijing may still suffer from insufficient iodine intake. Abbreviations CV coefficients of variation HPLC high-performance liquid chromatography ICP-MS inductively coupled plasma mass spectrometry KED kinetic energy discrimination KI potassium iodide LOD limit of detection S-K Sandell-Kolthoff reaction PUMCH Peking Union Medical College Hospital.