Feasibility Study Of Salivary Iodine For The Assessment Of Iodine Nutritional Status In Women During Pregnancy

Objectives: 1.To assess the iodine nutritional status,iodine intake and thyroid function of pregnant women in Xinjiang;2.The value of urine iodine concentration(UIC),urine iodine and creatinine ratio(UI/Cr),saliva iodine concentration(SIC)and serum total iodine(St I)for the diagnosis of iodine insufficiency,excess and abnormal thyroid function;3.To explore the feasibility of salivary iodine for assessing the iodine nutritional status of women during pregnancy and to provide a basis for a reference range of salivary iodine values for women during pregnancy.Methods: The representative southern Xinjiang Aksu region and the northern Xinjiang Yili Kazakh Autonomous Prefecture(Yili Prefecture)were selected as survey areas.Aksu city,Wensu county and Kuche city in Aksu region,and Yining city,Yining county,Huocheng county and Zhaosu county in Yili Prefecture were randomly selected as survey sites,and local pregnant women were selected as survey respondents according to the inclusion and exclusion criteria.The mean daily dietary iodine intake level of women during pregnancy was assessed by a questionnaire survey of basic information on women during pregnancy by means of a 3-day,24-hour dietary recall method;Collection of urine,saliva,and blood samples from pregnant women to test for urinary iodine,urinary creatinine,salivary iodine,serum iodine and thyroid function indicators;Ultrasound measurement of thyroid volume(Tvo L)and nodules in women during pregnancy.Results:(1)A total of 1207 pregnant women were included in this survey,603 in Aksu region and 604 in Yili Prefecture,with 238,518 and 451 in each of early,middle,and late pregnancy.The UIC M(IQR)was 177.86(106.10,265.71)μg/L,UI/Cr M(IQR)was 234.75(133.38,378.23)μg/g,SIC M(IQR)was 78.84(30.73,166.79)μg/L and St I M(IQR)was 89.78(72.86,109.90)μg/L.According to the WHO criteria for urinary iodine in pregnant women,the overall iodine nutrition status of pregnant women is appropriate.(2)The average daily iodine intake of pregnant women from drinking water,salt,food,and total diet was 3.91(1.95,5.92)μg/d,235.30(223.67,268.40)μg/d,51.87(32.42,109.73)μg/d and 301.11(267.72,368.15)μg/d respectively.According to the Chinese Dietary Reference Intakes for Nutrients-Part III: Trace Elements,the overall iodine intake for pregnant women is 230～600 μg/d.(3)The area under the ROC curve for salivary iodine for the diagnosis of inadequate and excessive iodine intake was higher than for urinary iodine,urinary iodine to urinary creatinine ratio and serum iodine(P <0.05).The area under the ROC curve for salivary iodine to diagnose inadequate iodine intake was 0.725(P <0.001),with a best cut-off value of 62.16 μg/L and a Jorden index of 0.365;the area under the ROC curve for salivary iodine to diagnose excess iodine intake was 0.732,with a best cut-off value of 137.45 μg/L and a Jorden index of 0.389.When the salivary iodine level was less than 62.16 μg/L,the OR for inadequate iodine intake in pregnant women was3.13(95% CI: 1.84,5.33);when the salivary iodine level was >137.45 μg/L,the ORs for UIC <150 μg/L,inadequate iodine intake,excessive iodine intake and abnormal thyroid function in pregnant women were 0.68(95% CI.0.49,0.94),0.43(95% CI: 0.19,0.99),3.69(95% CI: 1.73,7.86)and 3.70(95% CI: 1.27,10.75)respectively(P <0.05).(4)Regression analysis of salivary iodine quartiles showed that the higher the salivary iodine quartile,the greater the regression coefficient for UIC and total dietary iodine intake levels,and that there was always a positive correlation between UIC,total dietary iodine intake levels and salivary iodine levels.(5)The 95% medical reference range for overall SIC levels in pregnant women is 6.26～508.86 μg/L.As SIC levels increase,UIC,salt iodine intake,dietary iodine intake and total dietary iodine intake show an increasing trend,and Tvo L shows a decreasing trend.Conclusion: The overall iodine nutritional status and iodine intake levels of pregnant women are appropriate;salivary iodine levels in pregnant women are positively correlated with total dietary iodine intake and urinary iodine concentration;the optimal cut-off values for salivary iodine to diagnose inadequate and excessive iodine intake are 62.16 μg/L and 137.45 μg/L,respectively.The present study suggests that salivary iodine levels can be used as a potential indicator of the nutritional status of women during pregnancy,but the reference range of salivary iodine levels needs to be further investigated.