Objectives To understand the iodine nutritional level, provide reference for improving the iodine nutritional status, and to provide a theoretical basis for the iodine supplementation strategies of children in Xigu District of Lanzhou City from 2017 to 2018.

Methods By stratified sampling, 400 school-age children aged (8~10) years were randomly sampled from Xigu district of Lanzhou City. Their urine samples collected randomly at one time and family-type edible salt samples were collected and their iodine content was determined. Their iodine nutritional status, iodized salt coverage and its qualified rate were analyzed. Urine iodide was determined by arsenic-cerium catalytic spectrophotometry, and salt iodide content was determined by direct titration, respectively.

Results Analysis of iodine nutrition levels of children in Xigu District of Lanzhou City from 2017 to 2018 showed:① The median urinary iodide levels of children in Xigu District of Lanzhou City in 2017 and 2018 were between 200 and 300 μg/L, indicating their iodine intakes were sufficient. The non-parametric Wilcoxon rank sum test showed that a statistically significant difference in the median urinary iodine between these two years (Z=-3.23, P < 0.01). There was no significant difference in urinary iodide (< 100 μg/L or >300 μg/L) between boys in 2017 and 2018 (Z=-0.277, P>0.05 or Z=-1.111, P>0.05). There was no significant difference in the median urinary iodine < 100 μg/L between girls in 2017 and 2018 (Z=-0.441, P>0.05), but there was a statistical difference in the median urinary iodine of girls >300 μg/L (Z=-2.293, P < 0.05). ② The median salt iodine content of children in Xigu District of Lanzhou City in 2017 and 2018 was between 21 and 39 mg/kg, and their iodized salts were qualified. There was no significant difference in the median salt iodine between these two years (Z=-0.987, P>0.05). According to the χ² test, the difference in the qualified rate of iodized salt for children in Xigu District of Lanzhou City in 2017 and 2018 was statistically significant (χ²=278.276, P < 0.01). There was no significant difference in the total iodized salt coverage of children in Xigu District of Lanzhou City between 2017 and 2018 (χ²=380.000, P>0.05). ③ According to Spearman rank correlation analysis, there was no correlation between urinary iodine and salt iodine content in children (r=0.055, P>0.05) in 2017, but there was a negative correlation between urinary iodine and iodized salt content in children in 2018 (r=-0.287, P < 0.01).

Conclusions From 2017 to 2018, the iodine intake of children in Xigu District of Lanzhou City was excessive, and the urinary iodine median of girls >300 μg/L was different between the two years. The qualified rate of children's iodized salt was lower than the national standard. Therefore, the knowledge of iodized salt should be popularized, and the utilization rate of qualified iodized salt should be improved, in order to prevent the occurrence of iodine deficiency disorders, and to improve the health status of the whole population.