Reliability of Serum Assays of Iron Status in Postmenopausal Women

Purpose The aim of the study is to determine the reliability during a 2-year period of several newly developed iron-related assays to assess their potential for use in prospective epidemiologic studies. Methods We assessed the temporal reliability of several iron-related assays by using three serum samples collected at yearly intervals from 50 postmenopausal participants in a large prospective study. Results We observed high reliability coefficients for ferritin (0.78; 95% confidence interval [CI], 0.67–0.86), soluble transferrin receptor (sTfR; 0.79; 95% CI, 0.69–0.87), sTfR/ferritin ratio (0.74; 95% CI, 0.62–0.83), and hepcidin (0.89; 95% CI, 0.84–0.94). In a subset of 30 women, lower reliability was observed for serum iron (0.50; 95% CI, 0.29–0.70), unsaturated iron-binding capacity (0.55; 95% CI, 0.34–0.73), total iron-binding capacity (0.60; 95% CI, 0.40–0.76), and serum transferrin saturation rate (0.44; 95% CI, 0.22–0.65). The reliability of anti-5-hydroxymethyl-2′-deoxyuridine autoantibody titers, a biomarker of oxidized DNA damage, one of the mechanisms by which iron is thought to impact disease risk, was very high (0.97, 95% CI, 0.5–0.99). Conclusions Our results show that some newly developed iron-related assays could be useful tools to assess iron–disease associations in prospective cohorts that collect a single blood sample.