Zinc Protoporphyrin Past, Present, and Futurea

Abstract

The course of zinc protoporphyrin research has progressed at an increasingly rapid pace on several fronts. A variety of biochemical and clinical evidence viewed in toto now suggests that ferrochelatase catalyzes zinc protoporphyrin formation in states of relative iron-deficient erythropoiesis and in lead-inhibited iron metabolism. Furthermore, a redefinition of the relationship of zinc protoporphyrin to certain other parameters of iron status has been made based upon changes during the earliest states of iron depletion. These clinical studies show that the zinc protoporphyrin level and the ferritin level vary in concert but that changes in the percent transferrin saturation and in the hematocrit results are less consistent. Thus zinc protoporphyrin and ferritin are closely linked metabolically such that iron-deficient erythropoiesis becomes an initial manifestation of iron depletion. The measurement and expression of results as mumoles zinc protoporphyrin/mole heme have improved the quality of results, partly by the elimination of the assumed hematocrit designed into existing instruments. Other refinements in hematofluorometry technology have permitted exploration of the potentially extensive applications of zinc protoporphyrin measurements for lead surveillance and diagnosis, blood banking, pediatrics, obstetrics, sports medicine, and other clinical situations where a very sensitive, cost-effective indication of iron status is required.

Zinc protoporphyrin/haem ratio and plasma ferritin in preterm infants

“…15 The former view does not explain the good correlation between ZPP/H and plasma ferritin in adults over a wide range of ferritin concentrations. 12 14 We have shown that subjects with higher ZPP/H levels tend to have lower plasma ferritins, although changes in ZPP/H, for a given subject, did not correlate significantly with changes in plasma ferritin.…”

Iron Sulfate Supplementation Decreases Zinc Protoporphyrin to Heme Ratio in Premature Infants

“…In adults, this ratio is sensitive and will detect iron-deficient erythropoiesis as a result of either absolute or functional iron deficiency. [12][13][14][15] We recently determined population reference ranges for normally grown infants from 24 weeks to term gestation at the University of Washington Neonatal Intensive Care Unit (NICU). 16 The data suggested that both transfusions and iron sulfate supplementation correlated with decreased ZnPP/H.…”

Utility of zinc protoporphyrin in management of whole blood donors

“…As a consequence ZPP levels started to increase after 3 to 4 weeks. Since, during this period, decreases in hematocrit (Hct) levels were small and inconsistent, this suggests that ZPP may be a more early indicator for iron loss than Hct . These observations were further corroborated by a study that showed that ZPP values increased when depleted iron stores lead to iron‐deficient erythropoiesis, although Hb values were still within reference range .…”