Comparative effectiveness of zinc protoporphyrin and hemoglobin concentrations in identifying iron deficiency in a group of low-income, preschool-aged children: practical implications of recent illness.
OBJECTIVE
The goal was to assess the influence of recent infection on screening tests for iron depletion (zinc protoporphyrin and hemoglobin) among low-income, preschool-aged children.


METHODS
This cross-sectional study was conducted at community sites and ambulatory care clinics in Hartford, Connecticut, and included 180 preschool-aged children. Iron depletion was defined as serum ferritin levels of < or = 15 microg/L. Recent illness was defined by parent or guardian (caretaker) report or evidence of elevated C-reactive protein concentrations. History of anemia was determined through medical records review. Sensitivity, specificity and positive predictive values of hemoglobin and zinc protoporphyrin were calculated overall and for children with and without recent illness.


RESULTS
At enrollment, more than one half of the children had a recent illness, and 57.5% had a history of anemia. More than one third had iron depletion. Serum ferritin levels were significantly higher among recently ill children. Secondary to recent illness, the positive predictive value of elevated zinc protoporphyrin, but not low hemoglobin, was reduced significantly. Zinc protoporphyrin levels of >69 micromol/mol heme identified significantly more iron-deficient children.


CONCLUSIONS
Compared with anemia, elevated zinc protoporphyrin levels identified significantly more iron-deficient children. Recently ill children were one half as likely to have low serum ferritin levels, compared with children without recent illness. The negative effect of recent illness on the positive predictive value of zinc protoporphyrin when ferritin is used to determine iron status has many practical implications.
Crowell
Rebecca
R
Department of Nutritional Sciences, University of Connecticut, Unit 4017, 3624 Horsebarn Rd Extension, Storrs, Connecticut 06269, USA. rebecca.crowell@hotmail.com
Ferris
Ann M
AM
Wood
Richard J
RJ
Joyce
Patricia
P
Slivka
Hilda
H
D018798:Anemia, Iron-Deficiency / Q000175:diagnosis* / Q000453:epidemiology; D002675:Child, Preschool; D015897:Comorbidity; D003237:Connecticut / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D005293:Ferritins / Q000097:blood; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D007223:Infant; D007239:Infections / Q000453:epidemiology; D008297:Male; D008403:Mass Screening; D011203:Poverty; D011237:Predictive Value of Tests; D011524:Protoporphyrins / Q000097:blood*; D014505:Urban Population
D006454:Hemoglobins; D011524:Protoporphyrins; C017803:zinc protoporphyrin; D005293:Ferritins