Rapid inductively coupled plasma mass spectrometry method to determine iodine in amniotic fluid, breast milk and cerebrospinal fluid

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.