Evaluation of efficacy of iodine prophylaxis in Poland based on the examination of schoolchildren living in Opoczno Town (Lodz Voivodship)

Background In 1997 a currently obligatory model of iodine prophylaxis, based on mandatory iodization of household salt with 30 mg KI/kg, was introduced. The aim of our study was to assess the iodine intake among school-age children living in Opoczno in 3 subsequent time points – in 1994, before establishment of currently operating model of iodine prophylaxis, in 1999 – 2 years after implementation of iodine prophylaxis and in 2010, – 14 years after its implementation. Methods We assessed goitre incidence and urine iodine concentration (UIC) in 104 children in 1994, 207 children in 1999 and 174 children in 2012. Age of examined children ranged from 6 to 15 years. The thyroid volumes evaluated by ultrasound were compared to reference values for thyroid volume proposed by Zimmermann at al. Moreover, we have introduced a new index – V/BSA ratio (comparison of thyroid volume to the body surface area), which to our belief allows for more accurate assessment of thyroid volume. Results The median of UICs was 45.5 μg/L (1994), 101.1 μg/L (1999) and 100.6 μg/L (2010). The distribution of obtained results has changed as well – iodine concentrations below 50 μg/L were present in 59.1% children in 1994, in 12.6% children – in 1999 and in 7.1% children – in 2010. Although a significant decrease in goitre incidence with regard to age – 92.6% (1994) vs 18.5% (1999) and 15.8% (2010), as well as with regard to BSA – 95.4% (1994) vs 15.2% (1999) and 11.6% (2010) was observed, it still points to the iodine deficiency, which is in contradiction with UICs as they are within normal limits. V/BSA ratio avoids such discrepancy. The values of ratio V/BSA were higher in 1994 (7.079 ± 2.775) than in 1999 (2.935 ± 1.112) (p<0.05) and in 2010 (2.846 ± 1.029) (p<0.05). Conclusions Hitherto model of iodine prophylaxis has proved to be effective in eliminating the iodine deficiency. The iodine intake is now more even, homogenous, which translates into smaller scatter of UICs and less percentage of children, in whom UIC is less than 50 μg/L. However, the iodine intake only slightly exceeds the recommended values, so median of UICs oscillates around the lower limit of references values.