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When age really matters; ferritin reference intervals during infancy revisited
Sara Marie Larsson1,2, Andreas Hillarp1, Lena Hellström-Westas3
1Department of Clinical Chemistry, Hospital of Halland, Varberg Sweden.
Insights
Establishing accurate infant ferritin reference intervals is crucial for assessing iron stores. This study defined new reference limits for Swedish infants, revealing significant sex-based differences in ferritin levels by 12 months of age.
Area of Science:
- Pediatrics
- Clinical Chemistry
- Hematology
Background:
- Infants face risks of iron deficiency, complicating accurate assessment of iron stores.
- Establishing reliable reference intervals for ferritin, the primary marker for iron stores, in infants remains a clinical challenge.
Purpose of the Study:
- To establish robust reference intervals for serum ferritin in Swedish infants from birth to 12 months.
- To investigate potential sex differences in infant ferritin levels over the first year of life.
Main Methods:
- Serum ferritin levels were measured in 456 Swedish infants at birth, 48-72 hours, 4 months, and 12 months.
- Reference interval limits were determined using the 2.5th and 97.5th percentiles.
- Mathematical transformations and stringent measures were employed to minimize acute phase response interference and ensure precision.
Main Results:
- New lower and upper reference interval limits for infant ferritin were established.
- Sex differences in ferritin levels were confirmed, becoming more pronounced with age.
- By 12 months, boys exhibited a significantly higher upper 97.5th percentile for ferritin (56% higher) compared to girls.
Conclusions:
- The established reference intervals provide a valuable tool for assessing iron status in infants.
- Clinicians should be aware of the significant sex-based differences in ferritin levels, particularly in older infants, for accurate iron deficiency diagnosis.
Abstract:
Infants are at risk for iron deficiency. Despite research advances, assessing iron stores during infancy remains a challenge to the clinician. Ferritin is the first-choice laboratory marker for measuring iron stores but it is today still unclear how to evaluate reference intervals among infants. We have studied Swedish infants (n = 456), born at term after normal pregnancies. Ferritin was measured at birth (umbilical cord sample), 48-72 h, 4 months and 12 months. Lower and upper reference interval limits were constructed as the 2.5th and 97.5th percentiles. By a large study population, we were able to use more stringent measures to avoid interference from the acute phase response than previous reports on ferritin reference intervals. When we used mathematical transformation we furthermore avoided potential information loss in precision and confirmed earlier reports of sex differences. At the lower reference interval limits there were small differences between sexes. For the higher limits, the differences were more pronounced in the older infant. At 0-3 d of age we observed a difference between the sexes of only 5% at the upper limits. The differences peaked at 12 months, where the boys' upper 97.5th percentile was 56% compared to girls.
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