Objective Preterm infants have a lower incidence of allergies; however, data on serum levels of thymus and activation‐regulated chemokine (TARC/CCL17) are limited. We aimed to compare serum TARC levels at term‐equivalent age between preterm and term infants and examine their association with allergic outcomes. Methods We conducted a retrospective study of 1221 infants admitted to the neonatal intensive care unit between 2012 and 2018. Serum TARC levels were measured at 37–42 weeks’ term‐equivalent age. Infants were classified as preterm (extremely <28 weeks, very 28–31, or moderate‐to‐late 32–36), and term (≥37). Allergic outcomes at 6 years were assessed using International Study of Asthma and Allergies in Childhood (ISAAC)‐based caregiver questionnaires. Owing to the limited number of follow‐up responses, all preterm infants were analyzed collectively and compared with term infants. Results Median TARC levels increased with gestational age: 549, 689, 944, and 1242 pg/mL ( p < 0.001). Serum TARC levels were not associated with small‐for‐gestational‐age (SGA) status, sex, systemic corticosteroid use, antibiotic use, or emollient/topical therapy; did not differ significantly between inflammatory and noninflammatory neonates; and showed a weak positive correlation with eosinophil counts. At 6 years, preterm infants had lower atopic dermatitis (AD; p < 0.001) and higher bronchial asthma (BA; p = 0.003) prevalence, with no significant association between neonatal serum TARC levels and later allergic outcomes. Conclusions Preterm infants had lower serum TARC levels at term‐equivalent age, showing a gestational age‐dependent immune maturation gradient. No association was observed with later allergic outcomes. Their BA may include nonatopic wheezing phenotypes, warranting cautious interpretation.
Goto et al. (Thu,) studied this question.