Validation of a simple inductively coupled plasma mass spectrometry method for detecting urine and serum iodine and evaluation of iodine status of pregnant women in Beijing

Abstract

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

Keywords:

• Inductively coupled plasma mass spectrometry
• iodine
• pregnant women

Acknowledgments

The authors thank the engineer Zhi Li of Thermo Fisher in China for assistance in the use of ICP-MS.

The ICP-MS method for serum and urine iodine in this study has been selected as an oral presentation in the congress of Mass Spectrometry Applications to the Clinical Lab in Salzburg (MSACL 2016 EU).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the National Key Technology Research and Development Support program (2015BAI32H00) (http://program.most.gov.cn/), and by research grants from the National Natural Science Foundation of China (81702060) (http://www.nsfc.gov.cn/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors have no additional financial disclosures.