Method comparison of pediatric iron biomarkers: Implications for clinical interpretation across analytical platforms

Abstract

Iron deficiency is the most prevalent nutritional disorder in children and is typically assessed using serum iron, transferrin, and ferritin levels. However, variations in analytical methods between testing platforms may influence diagnostic accuracy and clinical decisions. This cross-sectional method comparison study evaluated 137 blinded pediatric serum samples collected from a tertiary children’s hospital in Vietnam. Serum iron was measured by a colorimetric method, transferrin by immunoturbidimetry, and ferritin by immunoassay, using two different platforms: Cobas Pro (Roche Diagnostics) and Atellica Solution (Siemens Healthineers). Analytical precision and trueness were assessed in accordance with CLSI EP15-A3 guidelines. Agreement between platforms was evaluated using Passing-Bablok regression and Bland-Altman analysis. Results showed systematic bias across all analytes, with the Atellica platform yielding consistently lower values. Specifically, the regression equations were Siemens = 0.96 (Roche) – 0.1 µmol/L for serum iron, Siemens = 0.93 (Roche) + 1.0 mg/dL for transferrin, and Siemens = 0.723 (Roche) – 1.7 µg/L for ferritin. Mean differences were -0.7 µmol/L, -15.6 mg/dL, and -137 µg/L, respectively. These findings indicate notable discrepancies between the platforms, underscoring the necessity for platform-specific reference intervals and the importance of harmonizing methods. In settings where harmonization is not feasible, regression-based adjustments may facilitate reference interval transference, especially in low-resource environments.