Specific reference interval for high-sensitivity cardiac troponin I among healthy children in Wuhan, China.

Background: Troponin (Tn) is of an important biomarker for the diagnosis and prognosis of myocardial injury and for evaluating the severity of cardiac involvement due to other systemic diseases in children. Unfortunately, high-sensitivity cardiac troponin I (hs-cTnI) specific reference intervals (RIs) are extremely limited. This study aimed to establish a preliminary pediatric hs-cTnI RI for newborns, children, and adolescents in Wuhan, China.

Methods: A total of 1,355 healthy participants (1 day to 19 years) were recruited from a cross-sectional study implemented in Wuhan Children's Hospital from September 2022 to August 2023. Serum hs-cTnI levels were detected via the Mindray automated chemiluminescence immunoassay analyzer (CL-6000i). Specific serum hs-cTnI RIs were established according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The RIs were defined by the nonparametric median (P50), and 2.5^th, 97.5^th [P50 (P2.5-P97.5)] intervals.

Results: Of the 1,355 pediatric participants, serum hs-cTnI concentrations of 1,332 children were measured. The serum overall P50 and 95% interval range (P2.5-P97.5) of serum hs-cTnI was 0.41 (0.00, 44.31) ng/L. This was higher in males of 0.47 (0.00, 44.90) ng/L than in females of 0.36 (0.00, 44.17) ng/L (P<0.01). Age- and sex-specific differences in hs-cTnI levels were observed. The levels were highly variable in children under 1 year of age (especially in newborns), deriving a P50 (P2.5-P97.5) of 22.06 (1.04, 154.22) ng/L, and gradually narrowed and decreased with increasing age, with a markedly lower established P50 (P2.5-P97.5) of 0.36 (0.00, 2.16) ng/L. However, the levels began to increase slightly at the age of 9-12 years and reached a small peak at the age range of 15 to 18 years in males with 0.71 (0.03, 3.29) ng/L, while females were less affected by puberty. Sex- and age-specific RIs for hs-cTnI were established: 5 age-specific RIs in males, 1 day-1 month: 30.16 (8.67, 171.81) ng/L; >1-12 months: 13.20 (0.63, 61.91) ng/L; >1-15 years: 0.36 (0.00, 1.86) ng/L; >15-18 years: 0.71 (0.03, 3.29) ng/L; >18-19 years: 0.52 (0.00, 1.92) ng/L; and 4 age-specific RIs in females, 1 day-1 month: 43.93 (18.82, 146.38) ng/L; >1-12 months: 5.22 (0.92, 42.54) ng/L; >1-6 years: 0.54 (0.00, 2.74) ng/L; >6-19 years: 0.23 (0.00, 1.56) ng/L.

Conclusions: This study preliminarily established age- and sex-specific serum hs-cTnI RIs using the Mindray CL-6000i system in healthy children in Wuhan, China.