Disparity of serum transferrin receptor measurements among different assay methods.

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.