Surveillance of iodine deficiency disorders in Tibet in 2011

Objective To monitor the situation of iodine deficiency disorders (IDD) in Tibet, and to provide a background information of iodine nutritional status of residents before adjustment of iodine concentration. Methods According to the method of population proportionate sampling(PPS), 27 counties were selected to carry out IDD surveillance. One primary school was selected in each county. Forty children aged 8-10 from each primary school were sampled to examine thyroid volume, and edible salt samples were collected from their home to determine salt iodine. In addition, 12 of the sampled children, 15 pregnant women and 15 lactating women from three townships near the selected schools were chosen to detect urinary iodine. The methods of B-ultrasonography, oxidation-reduction titration (GB/T 13025.7-1999) and arsenic cerium catalytic spectrophotometry (WS/T 107-2006) were used to determine thyroid volume, salt iodine and urinary iodine, respectively. Results One thousand and eighty-one children aged from 8 to 10 were examined, and their goiter rate was 1.9% (20/1 081). Seven hundred and fifty-eight salt samples were determined, and the median salt iodine level was 38.3 mg/kg and the consuming rate of qualified iodized salt was 88.1%(758/668). Meanwhile, urine samples of 522 children aged 8-10, 267 pregnant women and 336 lactating women were also tested, and their median urinary iodine level was 166.1, 132.7, 138.1 μg/L, respectively. Conclusions The results show that the goiter rate and urinary iodine level of children aged from 8 to 10 have reached the national standard of IDD elimination(< 5%, 100- 300 μg/L), while the residents consumption rate of qualified iodized salt is still lower than the national standard(90%). In particular, the iodine nutrition of pregnant women is inadequate, which is lower than the national standard(urinary iodine 150 μg/L). It is still necessary to strengthen the monitoring of salt iodine as well as iodine nutrition in special groups in the future, and strengthen health promotion at the same time. Key words: Tibet; Iodine deficiency disorders; Surveillance; Urinary iodine; Goiter, endemic