Abstract
BACKGROUND: Serum cancer antigen 125 (CA-125) is widely used in the diagnosis and follow-up of ovarian cancer, but its reference interval may vary between populations. We aimed to establish sex- and age-specific reference intervals for serum CA-125 in healthy Han Chinese adults receiving routine health checks, following CLSI C28-A3 guidance. METHODS: We reviewed health-check records from Shuyang Hospital and identified 10,076 Han Chinese adults aged 18-90 years whose serum CA-125 concentration was measured between October 2018 and December 2023. Individuals with self-reported or clinically documented chronic diseases, acute infection, pregnancy or abnormal results in complete blood count, liver and renal function tests, fasting plasma glucose or C-reactive protein were excluded. Serum CA-125 was measured on a DxI 800 chemiluminescent immunoassay analyser (Beckman Coulter). Statistical outliers were identified within sex and age partitions via Tukey's rule and, where needed, the Dixon test. Reference limits and 90% confidence intervals were estimated according to CLSI recommendations. RESULTS: After applying the clinical and laboratory criteria and removing 170 statistical outliers, 9,871 apparently healthy Han adults (7,688 females and 2,183 males) remained for analysis. The upper reference limit for CA-125 in men was 19.7 U/mL. In women, CA-125 concentrations were higher than those in men and were negatively correlated with age (Spearman r = - 0.2488, P < 0.001). The upper reference limits were 33.1 U/mL for women aged 18-30 years, 28.1 U/mL for those aged 31-70 years and 21.8 U/mL for those aged 71-90 years. CONCLUSIONS: Using a large health-check cohort and CLSI-based methodology, we established sex-specific and age-specific reference intervals for serum CA-125 in Han Chinese adults via the Beckman DxI 800 platform. In this population, CA-125 tends to decrease with age in women and remains relatively stable in men. These locally derived intervals may improve the interpretation of CA-125 in Han adults but should be verified in other centers, assay systems and ethnic groups.