Application Of Iodine-specific FFQ In Evaluation Of Iodine Nutrition In Pregnant Women

Objective1.To explore the rapid evaluation method of iodine nutritional status of pregnant women.2.To verify the feasibility of I-FFQ in iodine nutrition evaluation of pregnant women.3.Simplified and optimized the I-FFQ so that it can be better applied to individualized iodine nutrition evaluation system based on Internet.MethodsThe survey was carried out in Tianjin Women and Children Health Center,the subjects were pregnant women treated here.We protocolled the I-FFQ based on the pre-Tianjin residents nutrition and dietary survey,I-FFQ was used to investigate the dietary intake in the past six months,and the three-day dietary questionnaire was used to record the subjects’dietary intake of three consecutive days.Collect 5ml blood of pregnant women to measure the TSH、FT₃、FT₄、TPOAb、TGAb.The urinary iodine concentration and urinary creatinine concentration were measured in spot urine of the subjects and their spouses.The laboratory method for measuring urinary iodine concentration and creatinine is the arsenic-cerium catalytic spectrophotometry,and picric acid spectrophotometry.76 women of childbearing age in 20-29 years old were selected to conduct an I-FFQ survey twice a week under the guidance of unified training investigators at the Tianjin Medical University.Results1.The median urinary iodine concentration in pregnant women was 158μg/L,and in spouses was 178μg/L,the whole population were both in suitable iodine state,but there were 45.5%（228）of the pregnant women in the iodine deficiency state,17.6%（88）in more than adequate state,there were 3.2%（16）in iodine excessive state.2.The abnormal rates of FT₃,FT₄,TSH,TPOAb and TGAb were 6.43%,2.01%,1.81%,5.62%and 6.83%,the total abnormal rate was 18.5%.The abnormal rate of thyroid function in different urinary iodine concentration groups had no difference（FT₃:P=0.987,FT₄:P=0.996,TSH:P=0.208）.3.The average iodine intake was 328.7±87.0μg/d in the three-day dietary record and 348.1±95.9μg/d in the I-FFQ survey,the iodine intake of the whole population was adequate.4.Use result of the three-day dietary record as―calibration standard‖to make ROC curve of I-FFQ,The area under the ROC curve was 0.925（P<0.001）.The result of Kappa test shows good consistency（Kappa=0.518,P<0.001）.Bland-Altman plots analysis shows the mean variation of I-FFQ and three-day dietary questionnaire were 29.8μg/d,the consistency range was（-90.4¹50.0μg/d）,almost all the data are in the consistency range,the consistency is good.5.I-FFQ of childbearing age women results shows the interval of two weeks were related（r=0.826,P<0.001）.The mean difference of iodine uptake was 23.70μg/d.The result of the Kappa test of the twice I-FFQ indicating a good agreement（Kappa=0.762,P<0.001）.6.The correlation between I-FFQ and urinary iodine concentration in pregnant women was not statistically significant（P=0.381）,and was also no significant concentration after creatinine correction（P=0.350）.TherewasnocorrelationbetweenI-FFQandTSH,FT₃,FT₄（P=0.978,P=0.522,P=0.446）.There was no significant difference in thyroid hormone levels between different iodine intake groups（P=0.306,P=0.095,P=0.475）.7.Remove the food iodine contribution less than 0.1%.I-FFQ is optimized from the original 37 kinds of food to 16 kinds of food.The mean difference of iodine intake before and after optimization was 2.91μg/d,the difference before and after optimization was in the acceptable range,Kappa test results showed a good agreement（Kappa=1.000,P<0.001）.Conclusion1.The iodine iodine concentration in whole population was in the appropriate state,but there is still a large proportion in deficiency or excess state,urinary iodine concentration and thyroid function index are not related to iodine intake,so can not be used to evaluate individual iodine nutritional status.2.I-FFQ and three-day dietary questionnaire has high consistency,I-FFQ results of women in childbearing age showed good reproducibility,so,I-FFQ can be used as effective tool of individualized iodine nutrition evaluation.3.I-FFQ before and after optimized were highly consistent,so the optimized I-FFQ can be used for future iodine nutrition surveys for pregnant women and can be further applied to the Internet-based individualized iodine nutrition evaluation system.