Establishment of CA19-9 reference intervals in an apparently healthy adult population in Singapore.

Background: CA19-9 is elevated in pancreatic cancer and other malignancies, and commonly used in clinical practice. Unfortunately, CA19-9 immunoassays are not harmonized, and reference intervals may differ between assays. The aim of this study was to establish the reference interval of the ADVIA Centaur/Atellica IM CA19-9 assay in an apparently healthy Singapore adult population.

Methods: This is a retrospective cross-sectional study. De-identified data from Health Screening participants were extracted from our database. Subjects with biochemical results suggesting anaemia, diabetes mellitus, viral hepatitis or abnormal liver, and renal and tumour markers were excluded. Outlier and subclass analyses by age and sex were performed. CA19-9 reference limits and 90% confidence intervals were then determined for candidate subclasses.

Results: Data from 12,174 subjects (5846 males and 6328 females) were available after exclusion criteria were applied. CA19-9 results did not follow a normal distribution and were higher in females compared to males (P < .001). Although CA19-9 means were statistically different between certain age groups, the evaluable 99th percentile reference limits were not statistically different. The overall 99th percentile reference limits for the Centaur/Atellica CA19-9 assay was 37 U/mL for males 21-80 years, and 60 U/mL for females 21-80 years.

Conclusions: Our results suggest that separate CA19-9 reference intervals should be applied for males and females.