Determination of reference values for TREC and KREC in circulating blood of the persons over 18 years

Increasing attention is being paid to methods for detecting primary and secondary T and/or B cell immunodeficiencies. Their implementation into laboratory diagnostics would contribute to the early diagnostics of immunodeficiencies. Currently, the number of identified adult patients with immunodeficiencies of various origins is steadily increasing. Age, gender and ethnicity of patients may be significant factors of immunity. Hence, determination of the population reference intervals for TREC and KREC DNA excision rings in peripheral blood of adult persons is an urgent laboratory task for in-depth examination of both congenital and acquired immunodeficiency conditions. Our purpose was to determine the reference intervals for the quantitative assay of TREC and KREC fragments in peripheral blood among the adult population of St. Petersburg. We studied whole blood samples obtained from 717 apparently healthy volunteers aged 18 to 108 years within the program of population immunity assessment among residents of St. Petersburg. The exclusion criterion included immunodeficiency of any origin, viral hepatitis A, B, C, HIV infection. Quantitation of the target TREC and KREC DNA fragments was carried out using a set of reagents for the quantitative determination of excisional rings TREC and KREC by Real-time PCR (TREC/KREC-AMP PS). The reference intervals were determined by the direct method according to the recommendations of the International Federation of Clinical Chemistry and the Russian State Standard (GOST) R 53022.3-2008. The volunteers were divided into six age groups: 18-29, 30-39, 40-49, 50-59, 60-69 years old, and the persons over 70. The amounts of TREC and KREC in each blood sample were determined for all age groups. Upon correlation analysis, we have revealed a negative relationship between the concentration of TREC molecules in blood samples, and the age of study participants (Spearman correlation coefficient r = -0.80 (p-value < 0.0001)). Significant differences in TREC levels between different age groups were revealed. No correlations were detected between KREC contents in blood samples and age as well as any differences between age groups. Reference intervals of the TREC level were determined for each mentioned age group. A unified reference range was established for the KREC levels. The established reference intervals for TREC and KREC molecules in adults are significantly lower than in newborns. The obtained results enable determination of reference intervals for TREC and KREC levels among adults, thus contributing to effective personalized laboratory diagnosis of immunodeficiency states of various origins.