Over the past 100 years, public health authorities have estimated the severity of iodine deficiency using an evolving series of measures, first rooted in visible goiters and shifting a quarter century ago to emphasize IDD's role in brain development and mental retardation using measures of urinary iodine.

An important new study in the October issue of Nutrition Reviews, proposes a new method to estimate the prevalence of iodine deficiency using the estimated average requirement cut-point model. Authors ICCIDD executive director Michael Zimmerman and colleague Maria Andersson from the Institute of Food, Nutrition and Health, ETH, Zurich, Switzerland, affirm that urinary iodine concentration is an excellent biomarker of recent iodine intake in populations and is a more sensitive indicator of changes in iodine status than goiter.

Their study measures UIC in spot samples from population studies and defines Iodine status based on the median value which they compare to WHO reference thresholds. The question becomes how to use UIC to define iodine deficiency. Earlier approaches, posit Zimmermann and Andersson, may have overestimated the global prevalence.

This is a promising new approach to add to the present toolbox for urinary iodine survey data. It better defines the "true" prevalence of iodine deficiency from iodine survey data and allows more specific monitoring of global progress towards the goal of global iodine deficiency control.

Using the Swiss experience as an example, Zimmermann and Andersson show that the country with a world-class salt iodization program has a steady average 120 micrograms/day iodine intake, but current measurements would consider 36% of the population to be consuming inadequate amounts of iodine. Using the current method, they conclude:

"It overestimates the true prevalence of ID and has contributed to the perception of a global slowdown in progress to control ID when looking at trends in numbers affected rather than in changes in national iodine status based on the median UIC. Over the past decade, the number of countries with adequate iodine status based on the national median UIC has jumped from 67 to 105.

"During the same period, the global prevalence of SAC with low iodine intake has fallen only 6%, from 36% in 2003 to 30% in 2011. This method has resulted in the paradox that in 2011, 3 out of 4 children classified as having low iodine intake are living in countries that are iodine sufficient based on the national median UIC, while only 1 in 4 with low intakes are living in countries with inadequate national medians. In practical terms, continued use of this method to define the prevalence of ID will make the global goal of elimination of ID impossible to achieve."