Zinc protoporphyrin and iron deficiency in children: prevalence, trends, and response to therapy in an urban primary care center
Magge, Hema Natesh
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Background: The American Academy of Pediatrics recommends routine treatment of iron deficiency (ID) due to its potential adverse neurodevelopmental consequences. Optimal testing to diagnose ID without anemia remains unclear. Zinc protoporphyrin (ZPP) has been found to be a valid and inexpensive indicator of ID but is not routinely collected in clinical practices. Evidence suggests that low-income children are at high risk for ID. Objective: To 1) describe the prevalence of ID as measured by ZPP in a low-income population, 2) describe the natural history of ZPP over time, and 3) examine the relationship between iron prescription and ZPP and implications for screening. Design/Methods: This was a retrospective longitudinal study of data from the electronic medical records at Boston Medical Center from 1/1/02 to 12/31/10. Children with a baseline CBC drawn between age 8-18 months and routine screening results for CBC, lead, and ZPP at baseline and follow-up within 2 years were included. Children with sickle cell disease or elevated lead value (≥10 mcg/dL) were excluded. Multivariate logistic regression was used to determine the association between iron prescription and ZPP at follow-up. Results: Ofthe 2612 eligible children, 79% were publicly insured and 65% were Black. Overall, 48% of these children had an abnormal ZPP level (≥35 mcg/dL). Among those with an abnormal ZPP at baseline (n=1254), 18% were prescribed iron. Improvement in ZPP was found in both groups. Iron prescription was significantly associated with improvement in ZPP (OR 1.5, 95% CI 1.1-2.0) and greater mean change in ZPP (p=0.01). In the multivariate analysis, the effect of iron prescription on improvement in ZPP was modified by hemoglobin level. Among those with abnormal ZPP and anemia at baseline (n=189), interim iron prescription was significantly associated with ZPP improvement at follow-up (aOR 2.4, 95% CI 1.1-5.0). Among children without anemia, iron was rarely prescribed and no significant association with ZPP improvement was found. Conclusions: ID, as measured by elevated ZPP , was common in this low-income population, the majority of whom showed improvement at follow-up. Iron prescription was significantly associated with ZPP improvement. Our data suggest that ZPP may be an appropriate method for screening for ID and monitoring response to therapy.
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