Background The reference intervals for serum cytokeratin-19 fragment (CYFRA 21-1) have not been established in Chinese population. This study aimed to measure serum CYFRA 21-1 levels in healthy Chinese subjects. Methods This cross-sectional, four-center study in two Chinese provinces enrolled participants (aged 18 - 85 years) with normal liver/kidney function and normal results for routine blood tests/urinalysis. Serum CYFRA 211 level was measured by ARCHITECT immunoassay (Abbott Diagnostics). Results The study included 3,366 participants. The median (interquartile range) value for serum CYFRA 21-1 level was 1.38 (1.00 - 1.89) ng/mL and tended to increase with age. The upper limit of the 97.5th percentile was 3.55 ng/mL and tended to increase with age. Serum CYFRA 21-1 median level varied between the four centers from 1.22 (0.89, 1.71) to 1.55 (1.12, 2.18) ng/mL, while the 97.5th percentile varied from 3.24 to 4.09 ng/mL. CYFRA 21-1 level correlated weakly with age and creatinine level. Conclusions These new data can help to establish the 'normal range' of serum CYFRA 21-1 in people in China.
