title: Comparison of indicators of iron deficiency in Kenyan children.
abstract: BACKGROUND
  In the absence of a feasible, noninvasive gold standard, iron deficiency (ID) is best measured by the use of multiple indicators. However, the choice of an appropriate single iron biomarker to replace the multiple-criteria model for screening for ID at the population level continues to be debated.
  
  
  OBJECTIVE
  We compared ID defined as ≥ 2 of 3 abnormal ferritin (< 12 μg/L), soluble transferrin receptor (TfR; > 8.3 mg/L), or zinc protoporphyrin (ZP; > 80 μmol/mol) concentrations (ie, multiple-criteria model) with ID defined by abnormal concentrations of any of the independent candidate iron biomarkers (ferritin alone, TfR alone, or ZP alone) and TfR/ferritin index (ID, > 500). Values either were adjusted for inflammation [as measured by C-reactive protein (> 5 mg/L) and α(1)-acid glycoprotein (> 1 g/L) before applying cutoffs for ID] or were unadjusted.
  
  
  METHODS
  In this community-based cluster survey, capillary blood was obtained from 680 children (aged 6-35 mo) for measurement of iron status by using ferritin, TfR, and ZP.
  
  
  RESULTS
  On the basis of the multiple-criteria model, the mean (±SE) prevalence of ID was 61.9 ± 2.2%, whereas the prevalences based on abnormal ferritin, TfR, or ZP concentrations or an abnormal TfR/ferritin index were 26.9 ± 1.7%, 60.9 ± 2.2%, 82.8 ± 1.6%, and 43.1 ± 2.3%, respectively, for unadjusted values. The prevalences of ID were higher for adjusted values only for low ferritin and an elevated TfR/ferritin index compared with the unadjusted values. The κ statistics for agreement between the multiple-criteria model and the other iron indicators ranged from 0.35 to 0.88; TfR had the best agreement (κ = 0.88) with the multiple-criteria model. Positive predictive values of ID based on the other iron indicators in predicting ID based on the multiple-criteria model were highest for ferritin and TfR. Receiver operating characteristic curve analysis indicated that TfR (AUC = 0.94) was superior to the other indicators in diagnosing ID based on the multiple-criteria model (P < 0.001). The inflammation effect did not appear to alter these observations appreciably.
  
  
  CONCLUSIONS
  TfR better estimates the prevalence of ID in preschoolers than do ferritin, ZP, and the TfR/ferritin index on the basis of multiple indexes in a high inflammation, resource-poor setting. This trial was registered at clinicaltrials.gov as NCT101088958.
authors.affiliation: Nutrition and Health Sciences program of Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, GA 30322, USA. ebogrant5@yahoo.com
authors.forename: Frederick K E
authors.initials: FK
authors.lastname: Grant
authors.forename: Reynaldo
authors.initials: R
authors.lastname: Martorell
authors.forename: Rafael
authors.initials: R
authors.lastname: Flores-Ayala
authors.forename: Conrad R
authors.initials: CR
authors.lastname: Cole
authors.forename: Laird J
authors.initials: LJ
authors.lastname: Ruth
authors.forename: Usha
authors.initials: U
authors.lastname: Ramakrishnan
authors.forename: Parminder S
authors.initials: PS
authors.lastname: Suchdev
mesh_terms: D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D019540:Area Under Curve; D015415:Biomarkers / Q000097:blood*; D044383:Black People; D002097:C-Reactive Protein / Q000378:metabolism; D002675:Child, Preschool; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005260:Female; D005293:Ferritins / Q000097:blood / Q000172:deficiency; D006801:Humans; D007223:Infant; D007249:Inflammation / Q000097:blood; D019266:Iron, Dietary / Q000008:administration & dosage / Q000097:blood; D007630:Kenya / Q000453:epidemiology; D008297:Male; D015995:Prevalence; D011524:Protoporphyrins / Q000097:blood; D012372:ROC Curve
chemical_list: D015415:Biomarkers; D019266:Iron, Dietary; D011524:Protoporphyrins; C017803:zinc protoporphyrin; D002097:C-Reactive Protein; D005293:Ferritins