Objective: To highlight differences in the quantification of transferrin receptor (TfR) concentration (a reliable index of iron deficiency) between three different assay methods.
Design: Methods comparison of TfR measurements in 'elevated' and 'normal' human sera using the Ramco, Quantikine and 'Lab' assays.
Setting: The Hospital for Sick Children, Toronto, Ontario, Canada.
Subjects: Pooled TfR for elevated and normal human sera obtained from the Ramco TfR assay kit.
Main outcome measures: Differences between TfR concentrations in normal and elevated samples and repeatability for each assay method and limits of agreement in TfR quantification between assay methods.
Results: The mean TfR concentrations for the elevated reference serum samples was higher than the normal reference samples within each individual assay (P < 0.001); however, measurement agreement between methods was poor.
Conclusions: Recognition of the relative differences in the values obtained from each of the assays should affect the interpretation of TfR concentration as an index of iron deficiency.