Serum transferrin receptor and zinc protoporphyrin as indicators of iron status in African children.
BACKGROUND
Although transferrin receptor (TfR) and zinc protoporphyrin (ZnPP) are often used to define iron status in school-age children in developing countries, the diagnostic cutoffs for this age group are uncertain.


OBJECTIVE
The objective was to determine the sensitivity and specificity of TfR and ZnPP in predicting iron deficiency in black and white children in Africa.


METHODS
Hemoglobin, C-reactive protein (CRP), serum ferritin (SF), TfR, and ZnPP were measured in children in Côte d'Ivoire and Morocco. We excluded children with elevated CRP and then used receiver operating characteristic (ROC) curves to evaluate TfR and ZnPP alone and in combination in screening for iron deficiency, defined as an SF concentration <15 mug/L, and iron deficiency anemia (IDA), defined as an SF concentration <15 mug/L and low hemoglobin.


RESULTS
The sample included 2814 children aged 5-15 y. The sensitivity and specificity of TfR and ZnPP were limited by considerable overlap between iron-sufficient, nonanemic children and those with IDA. On the basis of ROC curves, we identified diagnostic cutoffs for TfR and ZnPP that achieved specificities and sensitivities of approximately 60-80%. Separate cutoffs for Côte d'Ivoire and Morocco gave the best performance; the cutoffs for both TfR and ZnPP were higher in Côte d'Ivoire. Moreover, a comparison of nonanemic, iron-sufficient subjects showed that Ivorian children had significantly higher TfR and ZnPP concentrations than did Moroccan children (P < 0.01).


CONCLUSIONS
New diagnostic cutoffs for TfR and ZnPP, based on ROC curve analyses, may improve the performance of these indexes in defining iron status in children. Significant ethnic differences in TfR and ZnPP suggest that separate cutoffs may be needed for black and white children.
Zimmermann
Michael B
MB
Human Nutrition Laboratory, Swiss Federal Institute of Technology, Zürich, Switzerland. michael.zimmermann@ilw.agrl.ethz.ch
Molinari
Luciano
L
Staubli-Asobayire
Franziska
F
Hess
Sonja Y
SY
Chaouki
Noureddine
N
Adou
Pierre
P
Hurrell
Richard F
RF
D000293:Adolescent; D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000175:diagnosis; D015415:Biomarkers / Q000097:blood; D044383:Black People; D002648:Child; D002675:Child, Preschool; D007560:Cote d'Ivoire; D004909:Erythrocyte Indices; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D000090463:Iron Deficiencies; D008297:Male; D009018:Morocco; D011237:Predictive Value of Tests; D011524:Protoporphyrins / Q000097:blood*; D012372:ROC Curve; D011990:Receptors, Transferrin / Q000097:blood*; D012015:Reference Standards; D012680:Sensitivity and Specificity; D044465:White People
D015415:Biomarkers; D006454:Hemoglobins; D011524:Protoporphyrins; D011990:Receptors, Transferrin; C017803:zinc protoporphyrin