Best Time to Start Screening for IDA in Infants
The correct answer is C - 12 months (specifically 9-12 months of age) for routine screening of iron-deficiency anemia in otherwise healthy term infants. 1, 2
Screening Timeline for Healthy Term Infants
For high-risk populations (low-income families, WIC-eligible, migrant or refugee children), universal screening should occur between 9-12 months of age, with repeat screening 6 months later (15-18 months), and then annually from ages 2-5 years. 1
For populations not at high risk, selective screening at 9-12 months is recommended only for infants with specific risk factors, including: 1
- Preterm or low-birthweight infants
- Infants fed non-iron-fortified formula for >2 months
- Infants introduced to cow's milk before 12 months
- Breastfed infants without adequate dietary iron after 6 months
- Children consuming >24 oz daily of cow's milk
Why 9-12 Months Is the Optimal Screening Age
The 9-12 month timeframe allows sufficient time for iron deficiency anemia to develop after birth iron stores are depleted (which occurs at 4-6 months) and dietary factors have had time to manifest. 1, 2
- Term infants are born with adequate iron stores lasting approximately 4-6 months 2
- Iron deficiency anemia generally does not occur until approximately 9 months in term infants 2
- Screening at 9-12 months (rather than earlier) provides adequate time for nutritional anemia to become evident after weaning from iron-fortified formula and for toddler dietary patterns to influence iron status 3
Why Earlier Screening Ages Are Incorrect
Screening at 2 months (Option A) or 4 months (Option B) is too early because: 2, 4
- Healthy term infants have sufficient iron stores from birth through the first 4-6 months
- There has not been sufficient time for iron deficiency anemia to develop, even with rapid growth rates 3
- These ages are only relevant for preterm/low-birthweight infants who require iron supplementation starting at 1 month 1, 2
Screening at 18 months (Option D) is too late for initial screening because: 1
- The critical window for detecting and treating IDA is 9-12 months when prevalence is highest
- 18 months represents the timing for the second screening (6 months after the initial 9-12 month screen) 1
- Delayed detection misses the opportunity for early intervention during a period of rapid neurodevelopmental growth
Critical Clinical Context
The American Academy of Pediatrics recommends universal screening for anemia at 12 months of age using hemoglobin, though this test has limitations in diagnostic accuracy for iron deficiency. 5, 6
A common pitfall is that hemoglobin screening alone has poor sensitivity (only 25%) for detecting iron deficiency compared to serum ferritin <12 μg/L, meaning many iron-deficient children will be missed if relying solely on hemoglobin. 5
Children aged 9-18 months are at highest risk for iron deficiency of any age group, with iron requirements of 0.9-1.3 mg/kg/day. 7
Supporting Evidence Hierarchy
The CDC guidelines 1 provide the most comprehensive and widely-adopted screening recommendations, specifying 9-12 months as the initial screening age. This is reinforced by AAP recommendations 6 and multiple research studies 3, 8, 5 that support this timing based on the natural history of iron deficiency development in infancy.