Conclusions
The present study used RT-qPCR to analyze TRECs levels in 475 healthy children of different ages in China. This is the largest population of healthy children to be analyzed in China. We established reference values for TRECs and quantified trends in TRECs levels according to age and sex. We provide solid data showing a correlation between CD4 naïve T cell counts and TRECs levels according to age. Postnatal factors such as nutrition and hormone levels induce rapid changes in the phenotype of CD4 naïve T cells. We also showed that TRECs levels are of clinical utility by quantifying them in patients with WAS, APDS, or STAT1 mutations, in patients post-HSCT, and in patients with secondary immunodeficiency disease. Although the methods used to measure and detect TRECs differ between laboratories (which will lead to differences in TRECs levels in the same individual), it is still meaningful to establish a TRECs reference value within a consistent environment. Our institution is the main PID diagnosis and treatment center in China; therefore, such a reference value system will enable prompt screening of PIDs in a timely manner.