Serum transferrin receptor, ferritin, and reticulocyte maturity indices during the first year of life in ‘large’ preterm infants

Abstract

Preterm infants are at risk of developing iron deficiency; among the iron status and hemopoiesis indices the serum transferrin receptor (sTfr) has been shown to be a useful indicator in assessing iron status, while immature reticulocyte production is regarded as an estimator of erythropoiesis. To investigate age-related changes in iron status infants born 'moderately' preterm, with a gestational age (GA) of 32-36 wk, and identify associations between sTfr and other hematological and biochemical iron indices. Hospital-based prospective, longitudinal study in preterm infants. Iron and erythropoiesis parameters were evaluated in 181 formula-fed preterm infants at 2 and 6 wk and 3, 6, 9, and 12 months chronological age. Hemoglobulin (Hb), hematocrit (Hct), mean corpuscular volume (MCV), reticulocytes, serum iron (sFe), serum ferritin (sFer), sTfr, and reticulocyte subpopulations were measured. A total of 756 measurements were performed. After an initial decline, Hb rose from month 3 to 12 of life. SFe and sFer and immature reticulocyte count decreased from the second week to the third month and remained stable thereafter. STfr was lower up to 6 wk and stable from month 3 to 12. Iron deficiency anemia (IDA) was found in 5.5% of infants. In 76 measurements sFer was <12 microg/L, implying storage iron deficiency (SID). A negative correlation was observed between sTfr and other indices of iron status such as Hb, Hct, MCV, sFe, and sFer. Infants with sFer <12 microg/L had lower sTfr than those with sFer >12 microg/L. Reticulocyte production was positively associated with STfr, but this association was dependent on the chronological age of the infant. Iron depletion is common in formula-fed preterm (32-36 wk GA) infants between month 3 and 12 of life. STfr appears to be an indicator of iron status in preterm infants during the first year of life.