[Evaluation of analytical transferability between two methods for measuring serum iron levels using Ferrozine and...

Serum iron is a routinely ordered test for assessing iron metabolism. Among colorimetric assays, Ferrozine- and Ferene S-based methods are widely used; however, analytical differences may compromise result comparability across platforms. This study evaluated the analytical transferability of serum iron results between these two methods performed on different analyzers. In accordance with the CLSI EP09-A3 guideline, 40 serum samples were analyzed in duplicate using two colorimetric methods: Ferrozine on the Roche Cobas Integra 400+ and Ferene S on the DiaSys Respons 920. Method agreement was assessed using Passing-Bablok regression, Bland-Altman analysis, and clinical concordance analysis. Mean serum iron concentrations were slightly higher with the Ferene S method than with the Ferrozine method, with a statistically significant paired difference (p = 0.001) and very high clinical concordance (κ = 0.91). The two methods were strongly correlated (r = 0.992; p < 0.001) and showed a constant bias of -0.845 (95% CI: -1.672 to -0.043). Bland-Altman analysis demonstrated a mean bias of -0.99 μmol/L with narrow limits of agreement (-2.08 to +0.09 μmol/L). The relative bias (-6.15 %) remained well below the predefined analytical tolerance threshold. Ferrozine and Ferene S based assays showed satisfactory analytical transferability and can be used comparably for serum iron measurement under the evaluated conditions.