Trends in TRECs levels in healthy children according to age and gender
We hypothesized that understanding trends in TRECs levels in healthy children according to age will help us to identify disease at the early stages; therefore, we quantified TRECs levels in 475 healthy children, including premature newborns and low weight newborns. In accordance with a previously published paper18, the children were categorized into seven different age groups (0–1 months (m), 1 m–6 m, 6 m–1 years (y), 1–4 y, 4–8 y, 8–12 y, and 12–18 y) (Table 1). TRECs levels fell significantly with increasing age (r -0.5179; p<0.0001) (Fig. 1), which is consistent with the findings of Ou et al19. TRECs declined rapidly from 1 m to 4 y and from 12 y to 18 y. There were no obvious changes between newborns and babies aged 1–6 m. Females tended to have higher levels of TRECs than males before the age of 1 year; however, the difference was not statistically significant. After the age of 1 year, TRECs levels in females were similar to those in males (Fig. 2).
We also analyzed TRECs levels according to gestation age (GA) (Fig. 3A). TRECs levels increased with the increasing GA. Levels in preterm infants were significantly lower than in full term babies (Fig. 3B), which is consistent with the findings of de Felipe et al20. Here, we found that full term newborns with low BW had lower TRECs levels than those of normal BW (Fig. 3C). However, the TRECs levels in preterm infants with low BW were comparable with those of normal BW infants (Fig. 3D).