The Feasibility Of Iodine-specific FFQ To Evaluate The Iodine Nutrition Status Of Pregnant Women

Objective 1)Three day diet review and 24-hour urine iodine excretion were used to verify the feasibility of the simplified food frequency questionnaire for pregnant women to evaluate the iodine nutrition status of pregnant women.2)A simplified food frequency questionnaire for pregnant women was used to estimate the iodine nutritional status of pregnant women.3)Compare the differences between different methods of estimating iodine intake.Methods The survey area of this study is Tianjin Binhai New Area and Gaoqing County,Shandong Province.A total of 2501 pregnant women were included.The questionnaire includes basic information,I-FFQ,and a three-day diet review questionnaire.Based on the basic information,pregnant women who meet the inclusion exclusion criteria were screened.I-FFQ is used to investigate the dietary intake of pregnant women in the past six months.Three-day diet retrospective questionnaire was used to survey all diets of pregnant women three days before the survey.Urine,blood samples,and household drinking water and salt samples were collected,and random urine and 24-h urine iodine concentrations,urine creatinine concentrations,thyroid function indicators,and thyroid volume were measured to evaluate the iodine nutrition status and thyroid function of pregnant women.Analyze the consistency of I-FFQ with the three-day diet review survey and the estimated iodine intake of 24h urinary iodine excretion,verify the feasibility of the simplified version of I-FFQ for evaluating the iodine nutrition status of pregnant women,and compare the differences of three methods of estimating iodine intake.Results The median urine iodine concentration was 154μg/L,and the urine iodine creatinine ratio was 119μg/g.The iodine nutritional status of pregnant women is appropriate.Serum FT₃ level was 4.19pmol/L,FT4 was 14.95pmol/L,TSH was 1.48m IU/L,Tg was 10.9μg/L,TPOb antibody positive rate was 9.8%,and TGAb antibody positive rate was 9.0%.Measured thyroid volume was 9.6（7.8,11.5）m L.The estimated dietary iodine intake of I-FFQ of pregnant women in Tianjin was 341μg/d,indicating sufficient iodine intake.The total iodine intake of I-FFQ and drinking water of pregnant women in Gaoqing,Shandong was 208μg/d,indicating that the iodine intake was insufficient.The 3-day dietary retrospective questionnaire measured the dietary iodine intake of pregnant women at 319μg/d.After Kappa consistency test,I-FFQ was in good agreement with the 3-day dietary retrospective survey（Kappa=0.76,P<0.001）,Bland-Altman consistency test results have a consistency range of-75.4 to 118.2μg/d,and5.0%of the data are outside the consistency limit,indicating that the consistency of two methods to assess dietary iodine intake is good.The estimated daily iodine intake of urinary iodine output at 24h was 215μg/d.After Kappa consistency test with I-FFQ,Kappa=0.281（P<0.001）,and 59%of the dietary iodine intake groups were consistent.In the Bland-Altman test,the average difference between the two methods for assessing iodine intake was 8.3μg/d,and the range of consistency was-638.5 to 655.1μg/d.4.6%of the individuals were outside the consistency limit.It shows that the two methods are consistent in assessing dietary iodine intake.The reproducibility of the two repeated dietary questionnaires was good,Kappa=0.618（P<0.001）,and 86%of the dietary iodine intake groups were consistent.In the Bland-Altman test,the average difference between the two methods for assessing iodine intake was-8.2μg/d,and the range of consistency was-182.1 to 165.7μg/d.7.8%of the individuals were outside the consistency limit.There was no difference in the prevalence of thyroid diseases under different iodine intake estimation methods,all of which could reflect the individual iodine nutritional status.However,I-FFQ was simple and easy,which could quickly and accurately evaluate the iodine nutritional status of pregnant women.Conclusion 1)The I-FFQ used in this study was in good agreement with the iodine intake estimated by the 3-day dietary review method and the urine iodine excretion amount at 24h,and the I-FFQ showed good reproducibility,which could be used to evaluate the iodine intake of pregnant women.2)The pregnant women included in this study were generally in an appropriate state of iodine nutrition,but there was still a double risk of iodine deficiency and iodine overdose.The proportion of iodine deficiency was higher in areas with high water iodine,and the recommended daily dietary iodine intake should be increased on the current basis.3)The three methods can accurately reflect the individual iodine nutrition,among which I-FFQ is a more convenient method to evaluate iodine intake.