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Correspondence

Indian Pediatr 2018;55: 1007

Concerns with Urinary Iodine Excretion Level in a Single Random Sample

 

Umesh Kapil1 and Ajeet Singh Bhadoria2

From 1Human Nutrition Unit,  AIIMS, New Delhi; and 2Department of Community and Family Medicine, AIIMS, Rishikesh, Uttarakhand; India.
Email: [email protected]

 


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.

 

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