Zinc protoporphyrin/haem ratio and plasma ferritin in preterm infants.

OBJECTIVE To study the utility of the zinc protoporphyrin/haem (ZPP/H) ratio as a measure of iron status in healthy, growing, preterm infants. METHOD ZPP/H was measured in 109 well, preterm infants from the time of hospital discharge until 1 year of age (637 determinations). RESULTS ZPP/H was initially high, but steadily declined. This was opposite to what was expected from the known changes in iron stores during the first year of life and the observed changes in plasma ferritin. Subjects with higher ZPP/H ratios tended to have lower ferritins, but changes in ZPP/H in a given subject were poorly reflected by changes in plasma ferritin. Between 6 and 9 months of age, ZPP/H correlated with other measures of iron status, but serum ferritin concentration did not. CONCLUSION Use of the ZPP/H ratio as a measure of iron status during the first year of life appears to be confounded by the developmental changes in ZPP/H, but in the later half of this period it may be a better measure of iron status than serum ferritin.