Reference values for spot urinary iodine concentrations in iodine-sufficient newborns using a new pad collection...

Area of Science:

• Pediatric Nutrition
• Biochemical Monitoring
• Public Health

Background:

• Infant iodine deficiency can negatively impact neurocognitive development.
• Limited indicators exist for assessing iodine intake in newborns.
• High access to newborns in maternity clinics presents an opportunity for early assessment.

Purpose of the Study:

• To develop and validate a simple pad system for collecting infant spot urine samples for iodine analysis.
• To establish reference ranges for urinary iodine concentration (UIC) in newborns within the first week of life.
• To aid in monitoring iodine nutrition status in early infancy.

Main Methods:

• A two-stage cluster sampling method was employed to select a national sample of healthy, term Swiss infants (n=634).
• Spot urine samples were collected on two consecutive days from infants aged 0-5 days.
• Thyrotropin levels and gestational information were also collected.

Main Results:

• The pad collection system demonstrated good performance and acceptance in testing.
• The median urinary iodine concentration (UIC) in the total sample (n=1224) was 77 microg/L.
• UIC showed a gradual increase from day 1 to day 4, and the UI:creatinine ratio was not a reliable standardization method due to high creatinine variability.

Conclusions:

• The current WHO median UIC cut-off for iodine sufficiency (>100 microg/L) may be inappropriate for newborns in their first week.
• Establishing reference data for UIC in newborns is crucial for accurate iodine status assessment.
• A simple collection system and newborn reference data can improve the utility of UIC monitoring in infants.