Zinc protoporphyrin a marker for iron deficiency in low-income children

By Sally Robertson, B.Sc.Mar 6 2013

Researchers say that zinc protoporphyrin (ZPP) could be a useful measure for screening infants from low-income families for iron deficiency (ID), as well as for monitoring response to therapy, especially among children with anemia.

In a retrospective, longitudinal study of a pediatric population, abnormal ZPP levels (≥35 µg/dL) not only correlated with reductions in established markers of iron status, but they also improved when iron supplementation was prescribed.

"ZPP has been found to be a specific and sensitive measure of ID that is technically simpler and less expensive to measure than erythrocyte protoporphyrin," explain Hema Magge (Boston children's Hospital, Massachusetts, USA) and colleagues.

The team investigated whether ZPP may be appropriate for iron deficiency screening in a pediatric population of low-income children at high risk for ID due to factors such as low birthweight and poor nutritional status.

The researchers report that of 2612 children (aged 8-18 months) with baseline blood data available, 1254 (48%) had abnormal ZPP levels. However, the majority (84%) of these children were not anemic (hemoglobin [Hb] <11g/dL).

Of the children with abnormal ZPP at baseline, 230 (18.3%) were prescribed iron supplements for anemia.

As reported in JAMA Pediatrics, the baseline ZPP among these individuals was 52.3 µg/dL and this decreased significantly to 43.9 µg/dL at a follow-up assessment 10 months later. In addition, the mean baseline Hb level significantly increased, from 11.3 g/dL to 11.7 g/dL at follow up. Other markers for iron status such as red cell distribution width and mean corpuscular volume were also significantly improved after 10 months of iron supplementation.

Of the individuals with an abnormal ZPP but without iron prescribed for anemia, there was also a significant decrease from baseline in mean ZPP, from 45.4 to 41.3 µg/dL. Small but significant improvements in Hb and red cell distribution were also observed.

"Significant improvement was noted in almost all indicators for iron status in both children who were prescribed iron and not prescribed iron. However, the degree of improvement was greater in children who were prescribed iron."

Compared with the children who were not prescribed iron, the odds ratios (ORs) for reduced ZPP and improved Hb among those who were prescribed iron was 1.5 and 1.6, respectively.

"Our results suggest that ZPP could be useful in monitoring the response to therapy after iron is initiated."

"Further investigation is warranted to explore the effect of iron on ZPP when monitoring the response to therapy at nonanemic levels and whether iron therapy should be considered for children with low-normal HB and elevated ZPP," suggests the team.

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