Usefulness of serum transferrin receptor and serum ferritin in diagnosis of iron deficiency in infancy

Abstract

Background: The serum transferrin receptor (TfR) and the ratio of TfR to serum ferritin (TfR:SF) have been shown to be useful as early indicators of iron deficiency. Objective: The objective of this study was to evaluate the performance of TfR and TfR:SF in the assessment of iron deficiency in infants and to analyze age-related changes in both variables. Design: A total of 716 blood samples obtained from 515 healthy infants aged 8-15 mo were studied. Results: In 144 samples in which all other laboratory indicators of iron status were within the reference range, the median and 95% CI for TfR and TfR:SF were 8.5 mg/L (95% CI: 5.9, 13.5) and 497 (95% CI: 134, 975), respectively. TfR and TfR:SF were significantly correlated with the other laboratory indicators of iron status. Furthermore, as the severity of iron deficiency progressed, there was a gradual increase in mean TfR concentration (P < 0.00001; analysis of variance). The sensitivity of TfR > 13.5 mg/L and TfR:SF > 975 in the diagnosis of iron deficiency was 23.6% and 68.4%, respectively. The specificity was 98.3% and 63.3% for TfR and TfR:SF, respectively. The sensitivity and specificity of SF < 10 μg/L were 63.7% and 60.8%, respectively. Receiver operator characteristic analysis showed that TfR and TfR:SF were more accurate than was SF alone in the diagnosis of iron deficiency. Conclusions: TfR and TfR:SF showed age-related changes; TfR and TfR:SF appear to be better diagnostic tests for iron deficiency in infants than SF.