| Objective: Through comprehensive analysis of Shanxi province’s data in seven national iodine deficiency disorders(IDD) surveillance, to dynamically evaluate iodine nutritional status and the prevailing tendency of IDD, offering scientific basis for formulating measures of controlling and preventing IDD and making adjustment of intervention strategies.Methods: 1. A retrospective analysis was used to perform the investigation. Shanxi province’s data in national IDD surveillances performed in 1995, 1997, 1999, 2002, 2005, 2011, 2014 after universal salt iodination(USI) was collected. By population proportion sampling(PPS), 30 counties(cities, areas) were chosen annually and one primary school was randomly selected from each county by simple random sampling. 50 children aged from 8 to 10 in 2014 and 40 ones in other years were chosen randomly in each drawn primary school, half male and half female. In 2011 and 2014, 20 pregnant women were randomly sampled in the township(town, street) where each chosen primary school located. Thyroid volume of the children aged from 8 to 10 and the iodine content of edible salt in their home were detected. 12 ones were randomly selected from the 40 8 ~ 10 year-old children(but all in 2014) and their random urine samples were collected, with urine iodine concentration measured. In 2011 and 2014, a urine sample of 20 pregnant women was collected and the urine iodine was measured. “Criteria for elimination of iodine deficiency disorders”(GB 16006-2008) and the latest iodine nutrition criteria recommended by WHO/UNIC EF/ICCIDD were used to evaluate the elimination status of IDD and the iodine nutritional status. Because iodized salt judging standard had several changes since 1995, in order to facilitate the longitudinal comparison, we make a unified standard as (35±15) mg, salt iodine content greater than or equal to 20 mg/kg and less than or equal to 50 mg / kg was regarded as qualified iodized salt, salt iodine content greater than or equal to 5 mg / kg and less than 20 mg / kg was regarded as unqualified iodized salt, salt iodine content more than 50 mg / kg was also regarded as unqualified iodized salt, salt iodine content less than 5 mg / kg was regarded as non- iodized salt. Thyroid volume was detected by palpation in 1995 and palpation combined with B-ultrasonography after 1995.Ultrasound method was detected by Normal value of thyroid volume in children and adolescents(GB16398-1996), after 2007 according to Diagnostic criterion of endemic goiter(WS276-2007). Urinary iodine concentration was detected by arsenic cerium catalytic spectrophotometry(WS / T 107- 2006). Salt iodine content was tested by direct titration, while S ichuan salt and other reinforced edible salt by arbitration determination(GB / T 13025.7-1999). 2. The data from investigation and laboratory tests was recorded and summarized by EXC EL2007. All data was analyzed by SPSS 13.0 statistical software. Urinary iodine concentration and salt iodine content were non-normal distribution data, so they were indicated with median. Thyroid goiter rate, the coverage rate of iodized salt, the rate of qualified iodized salt and the consumption rate of iodized salt were signed with %. The median urinary iodine and the median salt iodine were analyzed by rank sum test. Thyroid goiter rate, the coverage rate of iodized salt, the rate of qualified iodized salt and the consumption rate of iodized salt were analyzed by R×C χ2-text. A P value of < 0.05 was considered statistically significant.Results: 1. The median salt iodine in seven surveillances was 29.1(1995), 43.0(1997), 48.7(1999), 31.8(2002), 31.6(2005), 30.5(2011), 24.1(2014)mg/kg respectively. There was no statistically significant difference between 2002 and 2005(χ2=0.263, P>0.05). 2. The coverage rates of iodized salt were 94%(1995), 98.03%(1997), 97.49%(1999), 98.19%(2002), 98.71%(2005), 97.63%(2011) and 95.41%(2014), There was statistical difference between 1995 and 1997, 1999, 2002, 2005, 2011(χ2 =24.017, 17.809, 45.502, 40.542, 19.521, respectively, P <0.0024), and statistical difference existed between 2014 and 1997, 1999, 2002, 2005, 2011(χ2 =12.914, 9.352, 25.337, 25.637, 9.271, respectively, P <0.0024). 3. The rates of qualified iodized salt were 72.61%(1995), 59.89%(1997), 44.80%(1999), 94.88%(2002), 96.79%(2005), 97.49%(2011) and 76.37%(2014). The difference was not statistically significant between 1995 and 2014, and so as between 2011 and 2005(χ2 =4.629, 0.969, respectively, P >0.0024). 4 The consumption rates of qualified iodized salt were 68.25%(1995), 58.71%(1997), 43.67%(1999), 93.17%(2002), 95.58%(2005), 95.18%(2011) and 72.86%(2014). The difference between 1995 and 2014, 2002 and 2005, 2002 and 2011, 2005 and 2011 was not statistical significant(χ2 =6.718, 0.899, 0.130, 0.254, respectively, P >0.0024). 5. The thyroid goiter rates of children aged 8-10 were 10.92%(1995), 7.58%(1997), 6.33%(1999), 3.00%(2002), 4.79%(2005), 2.66%(2011) and 3.87%(2014). There was no statistically significant difference between 1995 and 1999, 1995 and 2002, 1995 and 2005, 1995 and 2011, 1995 and 2014(χ2 =15.9929, 58.0836, 32.4232, 66.2044, 52.0884, respectively, P <0.0024) 6. The median urinary iodine of children was 199.0(1995), 361.0(1997), 407.5(1999), 275.4(2002), 245.4(2005), 274.6(2011), 224.6(2014) μg /L. Between 1995 and 2014, 2005 and 2014, 2002 and 2005, 2002 and 2011, 1997 and 1999, the difference was not statistically significant(χ2 =1.909, 2.904, 2.115, 1.491, 2.218, respectively, P >0.0024). 7. The median urinary iodine of pregnant women was 279.6 and 17.71 g / L in 2011 and 2014, with the iodine nutrition more than adequate level and at the appropriate level respectively. The difference was statistical different(H=153.890, P < 0.01).Conclusion: 1. The first stage of universal salt iodization(USI) was in 1995 to 1997. The first monitoring data after USI indicated that the median urinary iodine and the coverage rate of iodized salt increased rapidly, with iodine nutrition of the general population improved significantly. However because of lags of the regression of goiter rate, the goiter rate remained at a higher level of 7.58%. 2. The second stage of USI was in 1997 to 1999. The province coverage rate of iodized salt reached more than 95% and the median urinary iodine of children was at a level of excessive odine nutrition. Thyroid goiter rate of children decreased significantly compared to in 1995. The effects of USI on IDD controlling emerge. 3. The third stage of USI was in 1999 to 2011. For many years of high coverage rate of iodized salt, high rate of qualified iodized salt, high consumption rate of iodized salt and stable salt iodine content, which provided strong support for the elimination of IDD, the level of urinary iodine in population returned to below 300 μ g/L and thyroid goiter rate of children kept within 5% from 2002. 4. The fourth stage of USI was in 2011 to 2014. The median salt iodine dropped significantly. The iodine nutrition of the general population representative of children approached the optimum level and the urinary iodine of pregnant women was at an appropriate level. Thyroid goiter rate of population kept below 5% 5. The USI strategy has achieved significant social benefits in Shanxi province. |
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