Objective: To study the factors leading to the variation of children's total goiter rates, urine iodine and salt iodine in West China.
Methods: Design effect (DEFF) was used to evaluate the variation of indicators.
Results: DEFF of children's total goiter rate was about 3.0 in 9 provinces, and the proportion was 75.0%. The DEFF of urine iodine was 1.0 - 3.5 in 6 provinces, and the proportion was 50.0%. The DEFF of intake rate of qualified iodized salt was over 3.0 in 11 provinces. The DEFF of covering rate of iodized salt was about 3.0 in 4 provinces.
Conclusion: In order to provide scientific basis for IDD surveillance in China, other than bias due to methods of no-sampling, sample size should be further calculated in West China. Thus the main influencing factors of indicator variation could be measured with scientific and reasonable basis.