Elevated zinc protoporphyrin associated with thalassemia trait and hemoglobin E

Abstract

OBJECTIVE: Increased zinc protoporphyrin/heme (ZPP/H) ratio has been used in pediatrics to screen for iron deficiency and lead poisoning. This study was conducted to determine whether common hereditary hemoglobin disorders (α- and β-thalassemia traits, hemoglobin E) found in U.S. minority groups are associated with an increase in the ZPP/H ratio in an iron-sufficient population. METHODS: The database was compiled from hemoglobinopathy screens performed between 1987 and 1993 at a regional referral laboratory in Washington State. ZPP/H ratio and hemoglobin type were obtained for 326 subjects between the ages of 15 and 49 years of age who were iron sufficient (serum ferritin levels ≥50 μg/L). RESULTS: The mean ZPP/H ratio was significantly higher ( p <0.01) for subjects with β-thalassemia trait (87 ± 32 μmol/mol), α-thalassemia trait (73 ± 37 μmol/mol), and hemoglobin E disorders (73 ± 24 μmol/mol) than for subjects with normal hemoglobin values (60 ± 8 μmol/mol). Fifty-one percent of subjects with β-thalassemia trait, 22% with hemoglobin E, and 20% with α-thalassemia trait had elevated ZPP/H ratios (>80 μmol/mol), compared with only 1.5% with normal hemoglobin values. CONCLUSIONS: The ZPP/H ratio is elevated in common hereditary hemoglobin disorders that mimic the microcytic anemia of iron deficiency, even in individuals without associated nutritional iron deficiency. For children who are treated for presumed iron deficiency, failure of the ZPP/H ratio to return to normal after adequate iron treatment, especially if microcytosis persists, indicates that a hereditary hemoglobin disorder may be present. (J P EDIATR 1996;129:105-10)