Dynamic analysis of iodine nutritional status and rationality of urine specific gravity correction for urinary iodine of focused groups in Fujian Province

Abstract

Objective To understand the iodine nutritional status of children aged 8 to 10 years old and pregnant women in the new standard iodized salt pilot areas of Fujian Province, and to analyze the rationality of urine specific gravity correction for urinary iodine. Methods In the 3rd, 6th, 9th, 12th, 15th and 21th months after supplying of new standard iodized salt in March 2012, the first to sixth phases′ assessment were conducted in Xindian Town of Xiang′an District, Xiamen City and Yongfu Town, Xinqiao Town of Zhangping City, Longyan City. Totally 200 children aged 8 to 10 years old and 50 pregnant women were selected from each town, home salt samples and urine samples were collected, salt iodine, urinary iodine and urine specific gravity were tested. Salt iodine was detected by General Test in Salt Industry-Determination of (GB/T 13025.7-2012); urinary iodine was detected by Method for Determination of Iodine in Urine by As3+-Ce4+ Catalytic Spectrophotometry (WS/T 107-2006); urine specific gravity was detected by digital refractometer. Results From the first to sixth phases′ assessment, the iodized salt coverage rates of children aged 8 to 10 years old and pregnant women were > 95%, the edible rates of qualified iodized salt were > 90%. The measured medians of urinary iodine of children aged 8 to 10 years old were 216.7, 219.5, 188.1, 206.7, 209.2, and 201.0 μg/L, respectively; except the third phase′s assessment, which was in the iodine appropriate level (100-199 μg/L), the other five phases′ assessment were all higher than the iodine appropriate level (200-299 μg/L); the medians of urinary iodine of children aged 8 to 10 years old after urine specific gravity correction were 215.0, 213.6, 197.3, 202.9, 204.3, and 197.7 μg/L, respectively; there were no significant differences in urinary iodine between the measured and urine specific gravity correction (Z=-0.131, -0.183, -1.052, -1.180, -0.311, -0.368, P > 0.05). The measured medians of urinary iodine of pregnant women were 134.0, 132.2, 120.9, 115.6, 113.3, and 123.3 μg/L, respectively, which were in the iodine deficiency level (< 150 μg/L); the medians of urinary iodine of pregnant women after urine specific gravity correction were 207.3, 197.1, 168.8, 158.3, 171.8, and 181.7 μg/L, respectively; there were significant differences in urinary iodine between the measured and urine specific gravity correction (Z=-6.419, -6.406, -5.990, -6.648, -7.008, -8.034, P < 0.01). Conclusions The iodine nutrition of children aged 8 to 10 years old is appropriate in the new standard iodized salt pilot areas of Fujian Province, while that of pregnant women is mild iodine deficiency. Further research is needed to use urine specific gravity to calibrate the concentration of urinary iodine to assess the iodine nutritional level of the focused populations in the regions. Key words: Child; Pregnant women; Salts; Urine; Iodine; Urine specific gravity