The research article published in a recent issue of Indian
Pediatrics [1] highlighted the success of National Iodine Deficiency
Control Program in which universal salt iodization is an integral
activity. The investigators found a Total goiter rate (TGR) of
2.08%, median Urinary iodine excretion (UIE) level of 175 µg/L and
approximately 72% of subjects were consuming adequately iodized salt. In
this study, ‘on-the-spot urine’ samples were collected from children
and on the basis of this UIE level, proportion of children with mild,
moderate and severe iodine deficiency were reported.
We submit this interpretation is scientifically not
valid due to following:
1. WHO recommends that median UIE level estimated
from spot urine samples of individuals in a cluster is for
defining iodine status for the cluster/ population and is not
intended for individuals [2].
2. Defining iodine status at the individual level
remains challenging. At least ten spot urine samples or 24-hour
urine samples are needed to assess individual iodine status with 20%
precision [3]. The spot samples may be collected at any time of the
day, except the first morning samples. The random urine
samples should be spread over a time frame to cover potential
variations. UIE in spot samples varies substantially between days
and seasons [4], as a consequence of a circadian rhythm of iodine
excretion [5], and due to differences in fluid intake [6].
Therefore, a single spot UIE is not a suitable indicator for
individual assessment. Urinary iodine excretion (UIE) in 24-hour
collections is regarded as a better method to reflect an
individual’s true daily excretion.
References
1. Bali S, Singh AR, Nayak PK. Iodine deficiency and
toxicity among school children in Damoh district, Madhya Pradesh, India.
Indian Pediatr. 2018;55:579-81.
2. WHO UNICEF, ICCIDD. Assessment of Iodine
Deficiency Disorders and Monitoring Their Elimination. A Guide for
Programme Managers. 3rd ed. Geneva: WHO; 2007.
3. König F, Andersson M, Hotz K, Aeberli
I, Zimmermann MB. Ten repeat collections for urinary iodine from spot
samples or 24-hour samples are needed to reliably estimate individual
iodine status in women. J Nutr. 2011;141:2049-54.
4. Rasmussen LB Ovesen L Christiansen E. Day-to-day
and within-day variation in urinary iodine excretion. Eur J Clin Nutr.
1999;53:401-7.
5. Sackett-Lundeen L, Nicolau GY, Lakatua DJ,
Ehresman DJ, Dumitriu L, Plinga L, et al. Circadian and seasonal
variation in iodine excretion in children in an endemic goiter area.
Prog Clin Biol Res.1990;341A:689-98.
6. Vejbjerg P, Knudsen N, Perrild H, Laurberg P, Andersen S,
Rasmussen LB, et al. Estimation of iodine intake from various
urinary iodine measurements in population studies. Thyroid.
2009;19:1281-6.
