Soluble transferrin receptors and soluble transferrin receptor - ferritin index in a healthy African population of South Africa

Background: South Africa has a high incidence of iron deficiency and HIV / Aids. The soluble transferrin receptor (sTfR) is not an acute phase reactant as is ferritin, hence it is useful for the diagnosis of iron deficiency in the presence of inflammation or infection. Methods: To explore the use of sTfR and sTfR - log ferritin index in evaluating body iron status, we measured soluble transferrin receptors and indirect measures of iron stores in 371 healthy Africans. Results: We observed an inverse correlation between sTfR and log serum ferritin (r = - 0.17, P < 0.0001), as well as sTfR - log ferritin index and transferrin saturation (r = - 0.26, P < 0.0001). Subjects classified as having iron deficiency (serum ferritin < 30µg/L and transferrin saturation < 15%) had significantly higher sTfR concentrations when compared to subjects with normal serum ferritin and transferrin saturation 15 - 50%, (9.2 ± 6.9µg/ml and 5.0 ± 2.4µg/ml, P < 0.0001) respectively. The concentrations of sTfR were normal to increased (5.5 ± 3.2 µg/ml) in subjects who may be classified as iron deficient based on serum ferritin levels (serum ferritin levels less than 30 µg/L, but transferrin saturation 15 - 50%). However, the sTfR - log ferritin index was superior over sTfR values in differentiating between this group and subjects classified as normal, respectively, 4.6 ± 4.1 and 2.6 ± 1.2, P < 0.0001. No significant differences were observed between the iron overload group (serum ferritin raised) and normal subjects. Conclusion: Based on these results we suggest that sTfR - log ferritin index be used together with other parameters of iron stores in the diagnosis of iron deficiency, particularly when sTfR concentration results are equivocal.