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Enzyme immunoassay of lactoferrin in newborn term infants: reference values and influence of diet
1Biochemistry Department, Selly Oak Hospital Birmingham, UK.
Insights
Plasma lactoferrin levels are significantly higher in newborns compared to adults, offering a potential diagnostic marker for infant infections. These elevated levels persist for several weeks after birth.
Area of Science:
- Biochemistry
- Immunology
- Neonatal Medicine
Background:
- Plasma lactoferrin, an acute phase protein, plays a role in anti-infective processes.
- Accurate diagnostic tools for infant infections are crucial due to diagnostic challenges.
- Existing reference values for infant plasma lactoferrin were inadequate.
Purpose of the Study:
- To establish a reliable method for measuring plasma lactoferrin in infants.
- To determine reference values for plasma lactoferrin in healthy term infants.
- To compare infant lactoferrin levels with adult values.
Main Methods:
- Development of a solid-phase enzyme immunoassay for plasma lactoferrin.
- Assay validation demonstrating linearity up to 800 µg/L, high recovery (96-99%), and good precision (10-15% inter-assay).
- Measurement of plasma lactoferrin in term infants during the first 15 weeks of life.
Main Results:
- Established a sensitive and precise assay for plasma lactoferrin requiring minimal blood volume.
- Determined significantly higher mean plasma lactoferrin levels in term infants (385 ± 113 µg/L) compared to adults (122 ± 40 µg/L venous, 107 ± 73 µg/L capillary).
- Observed elevated lactoferrin levels in infants up to 11 weeks, normalizing by 15 weeks, with no difference based on feeding method.
Conclusions:
- The developed immunoassay provides a valuable tool for assessing plasma lactoferrin in neonates.
- Elevated plasma lactoferrin in newborns suggests a significant role in neonatal immunity.
- Lactoferrin levels in infants normalize over the first few months, indicating developmental changes.
Abstract:
Plasma lactoferrin is an acute phase protein which may have a variety of roles in the anti-infective process. As the diagnosis of infection in infants is particularly difficult, measurement of this protein could make a useful contribution, however previous reference values for infants were unsatisfactory. A solid phase enzyme immunoassay for plasma lactoferrin which required only a small specimen of blood was established. It was linear up to 800 micrograms/L, with a recovery of between 96 and 99%, and had a between batch precision of between 10 and 15%. Using this method we have determined the level of circulating lactoferrin in term infants during the first three weeks of life to be (mean +/- SD) 385 +/- 113 micrograms/L which is significantly (P less than 0.005) higher than that found in adults (venous plasma 122 +/- 40 micrograms/L; capillary plasma 107 +/- 73 micrograms/L). Plasma lactoferrin levels were still significantly higher than those in adults at weeks 7 and 11 (267 +/- 176 micrograms/L and 269 +/- 163 micrograms/L respectively) but not at week 15 (176 +/- 165 micrograms/L). There were no differences between infants fed breastmilk and those fed on infant formulas. These findings are discussed in terms of the possible origin and role of lactoferrin in the newborn.