Low iodine intakes are associated with goitre and other iodine-deficiency disorders (IDD) that have affected billions of people worldwide. We aimed to assess total goitre rate (TGR) and urinary iodine concentration (UIC) in schoolchildren between 2007 and 2015, percentage of iodized salt consumption by households, and salt iodine content at production, distribution and household levels in north-west Iran.

UIC assessed among schoolchildren in nine consecutive years; 240 schoolchildren aged 8–10 years selected by systematic random sampling each year in the West Azerbaijan Province.

Median UIC was >100 μg/l in all years. More than 50 % of children had iodine deficiency (UIC≤99 μg/l) in 2010 and 2011, while this rate was approximately 15–35 % in other years. Proportion with UIC below 50 μg/l was <20 % in all years except 2010 and 2011. Excessive UIC (≥300 μg/l) rate was between 5·4 and 27·5 %. TGR decreased from 44 % in 1996 to 7·6 % and 0·4 % in 2001 and 2007, respectively. Regular surveys from 2002 to 2015 showed that 98 % or more of households consumed iodized salt. Iodine level ≥20 ppm was observed in 87·5, 83 and 73 % of salt at production, distribution and household level, respectively (data from national study in 2007). The last national study in 2014 showed that median iodine level in household salt was 27 ppm.

Our focused data suggest that the universal salt iodization programme is improving the iodine status of schoolchildren in the West Azerbaijan Province of Iran. Reduction of TGR to less than 5 % in schoolchildren indicates successful elimination of IDD as a major public health problem.

The main indicator adopted to track universal salt iodization has been the coverage of adequately iodized salt in households. Rapid test kits (RTK) have been included in household surveys to test the iodine content in salt. However, laboratory studies of their performance have concluded that RTK are reliable only to distinguish between the presence and absence of iodine in salt, but not to determine whether salt is adequately iodized. The aim of the current paper was to examine the performance of RTK under field conditions and to recommend their most appropriate use in household surveys.

Standard performance characteristics of the ability of RTK to detect the iodine content in salt at 0 mg/kg (salt with no iodine), 5 mg/kg (salt with any added iodine) and 15 mg/kg (‘adequately’ iodized salt) were calculated. Our analysis employed the agreement rate (AR) as a preferred metric of RTK performance.

Twenty-five data sets from eighteen population surveys which assessed household iodized salt by both the RTK and a quantitative method (i.e. titration or WYD Checker) were obtained from Asian (nineteen data sets), African (five) and European (one) countries.

In detecting iodine in salt at 0 mg/kg, the RTK had an AR>90 % in eight of twenty-three surveys, while eight surveys had an AR<80 %. When the RTK was used for detecting adequately iodized salt, the AR decreased significantly, with only one of fourteen surveys achieving an AR>90 %.

The RTK is not suited for assessment of adequately iodized salt coverage. Quantitative assessment, such as by titration or WYD Checker, is necessary for estimates of adequately iodized salt coverage.

To assess the iodine status of Swiss population groups and to evaluate the influence of iodized salt as a vector for iodine fortification.

The relationship between 24 h urinary iodine and Na excretions was assessed in the general population after correcting for confounders. Single-day intakes were estimated assuming that 92 % of dietary iodine was excreted in 24 h urine. Usual intake distributions were derived for male and female population groups after adjustment for within-subject variability. The estimated average requirement (EAR) cut-point method was applied as guidance to assess the inadequacy of the iodine supply.

Public health strategies to reduce the dietary salt intake in the general population may affect its iodine supply.

The study population (1481 volunteers, aged ≥15 years) was randomly selected from three different linguistic regions of Switzerland.

The 24 h urine samples from 1420 participants were determined to be properly collected. Mean iodine intakes obtained for men (n 705) and women (n 715) were 179 (sd 68·1) µg/d and 138 (sd 57·8) µg/d, respectively. Urinary Na and Ca, and BMI were significantly and positively associated with higher iodine intake, as were men and non-smokers. Fifty-four per cent of the total iodine intake originated from iodized salt. The prevalence of inadequate iodine intake as estimated by the EAR cut-point method was 2 % for men and 14 % for women.

The estimated prevalence of inadequate iodine intake was within the optimal target range of 2–3 % for men, but not for women.

To compare the iodine status of pregnant women and their children who were sharing all meals in Bangalore, India.

A cross-sectional study evaluating demographic characteristics, household salt iodine concentration and salt usage patterns, urinary iodine concentrations (UIC) in women and children, and maternal thyroid volume (ultrasound).

Antenatal clinic of an urban tertiary-care hospital, which serves a low-income population.

Healthy pregnant women in all trimesters, aged 18–35 years, who had healthy children aged 3–15 years.

Median (range) iodine concentrations of household powdered and crystal salt were 55·9 (17·2–65·9) ppm and 18·9 (2·2–68·2) ppm, respectively. The contribution of iodine-containing supplements and multi-micronutrient powders to iodine intake in the families was negligible. Adequately iodized salt, together with small amounts of iodine in local foods, were providing adequate iodine during pregnancy: (i) the overall median (range) UIC in women was 172 (5–1024) µg/l; (ii) the median UIC was >150 µg/l in all trimesters; and (iii) thyroid size was not significantly different across trimesters. At the same time, the median (range) UIC in children was 220 (10–782) µg/l, indicating more-than-adequate iodine intake at this age. Median UIC was significantly higher in children than in their mothers (P=0·008).

In this selected urban population of southern India, the iodized salt programme provides adequate iodine to women throughout pregnancy, at the expense of higher iodine intake in their children. Thus we suggest that the current cut-off for median UIC in children indicating more-than-adequate intake, recommended by the WHO/UNICEF/International Council for the Control of Iodine Deficiency Disorders may, need to be reconsidered.

This first nationwide survey was undertaken to estimate the prevalence rates and severity of iodine deficiency disorders (IDD) and the proportion of households consuming iodized salt.

The country was stratified into two ecological zones and 30 clusters (primary schools) from each zone, including the required numbers of pupils, were selected randomly. A subsample of pupils provided urine and salt samples for the determination of urinary iodine excretion (UIE) and presence of iodate, respectively.

Yemen.

There were a total of 2984 pupils aged 6–12 years of whom 2003 were boys and 981 girls. The majority (1800) pupils were from the lowland/coastal areas (zone II) and the rest (1184) from the mountainous regions (zone I).

The total goitre rates (TGR) in the whole country, zones II and I were 16.8%, 31.1% and 7.4%, respectively. The TGR in zone I for males was 32.8% and 27.3% for females, while in zone II the corresponding rates were 8.1% and 5.9%, respectively, and the differences were not statistically significant. Only three cases of visible goitres were encountered. The median UIE levels in zones I, II and the whole country were 13.6, 18.9 and 17.3 μg dl−1, respectively. Based on UIE cut-off points recommended by WHO, IDD was severe in 4.7% of pupils in zone I and 2.6% in zone II. Mild and moderate IDD were found in 18.5% and 8.7% of the pupils respectively. Nearly 70% of the surveyed pupils had UIE values of > 10 μg dl−1 (no deficiency). Girls had relatively better iodine nutrition as suggested by higher levels of median UIE. In addition, across all age groups median UIE values were above 10 μg dl−1. Over half of the households consumed iodized salt.

Since the introduction of universal salt iodization in 1996 both the prevalence and severity of IDD in Yemen were reduced markedly and Yemen can now be classified as a country with a mild IDD problem. However, the low level of households consuming iodized salt may hamper the goal of IDD elimination.

The purpose of this trial was to compare three different iodine interventions.

School children aged 8–10 years were randomized into one of three groups: group A was provided with iodized salt by researchers with an iodine concentration of 25 ppm; group B purchased iodized salt from the market; and group C was similar to group B with the exception that they were given iodized oil capsules containing 400 mg iodine at the beginning of the study. Salt iodine content was measured bimonthly for 18 months and indicators of iodine deficiency were measured at baseline and 6, 9, 12 and 18 months after randomization.

The prevalence of abnormal thyroid volumes, based on the World Health Organization (WHO) body surface area reference > 97th percentile, was 18% at baseline and declined to less than 5% by 12 months in groups A and C, and to 9% after 18 months in group B. Results for goitre by palpation were similar. The median urinary iodine was 94 μgl−1 at baseline and increased in all groups to > 200 μgl−1 at the 6-month follow-up.

In this population of school children with initially a low to moderate level of iodine deficiency, the group receiving salt with 25 ppm (group A) was not iodine deficient on all indicators after 18 months of study. When the iodine content of the salt varied, such as in group B, by 18 months thyroid sizes had not yet achieved normal status.