Comparison of Serum TARC Levels at Term-Equivalent Age Between Preterm and Term Infants

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.

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.

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.

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.