Background: Folate (vitamin B9) is essential for DNA synthesis, red blood cell formation, and neural development, particularly during childhood. While folate deficiency is well-documented, limited research has explored how age and ethnicity independently influence serum folate concentrations in paediatric populations.The aim of this study was to investigate the relationship between age, ethnicity, and serum folate concentrations in children and assess the clinical need for age- and ethnicity-adjusted reference ranges.Method: A retrospective analysis was conducted on serum folate results from 1,544 paediatric patients (aged 0–17 years) tested at a tertiary hospital laboratory in London, UK. Measurements were obtained using the Architect assay (Abbott Diagnostics). Data on patient age, sex, and self-reported ethnicity (White, Asian or Asian British, Black or Black British, and Mixed) were collected. Folate concentrations were classified as deficient (<6.8 nmol/L), indeterminate (6.8 – 13.4 nmol/L), replete (13.4 – 45.3 nmol/L), or high (>45.3 nmol/L) based on established clinical thresholds. Statistical analysis was performed using non-parametric tests and linear regression to assess differences across age categories and ethnic groups.Results: Folate concentrations declined significantly with age (Spearman’s ρ = -0.535, p < 0.001), with the steepest decline occurring in the first five years of life. Across all age groups and both sexes, White patients had significantly higher serum folate concentrations compared to Asian or Asian British (p=0.003) and Black or Black British patients (p=0.007). Black or Black British (p < 0.001) demonstrated more significant declines in serum folate concentrations with age, compared to their White counterparts. Males had significantly higher folate concentrations than females (p < 0.001), though sex did not significantly affect the rate of decline. (graph)Conclusion: This study highlights the influence of age and ethnicity on serum folate concentrations in a large paediatric cohort. The findings suggest that a single reference interval may not be appropriate across all demographic groups.Tailored reference ranges accounting for age and ethnicity may improve the accuracy of folate status assessment and reduce the risk of underdiagnosing deficiency in minority populations.
