—To determine the usefulness of zinc protoporphyrin, as measured by the Helena Protofluor-Z hematofluorometer, for detecting elevated lead levels.
—Observational, descriptive review of laboratory records from a university toxicology laboratory.
—Inner-city university pediatric clinic and two affiliated community clinics in Chicago, Ill.
—Seven hundred seventy-five children younger than 7 years with paired lead-zinc protoporphyrin results.
—Fifty-six percent had lead levels of at least 0.48 μmol/L and 8% had lead levels of at least 1.21 μmol/L. The sensitivity, positive predictive value, and negative predictive value of a zinc protoporphyrin level of 70 μmol/mol of hemoglobin for detecting a lead level of 0.48 μmol/L were 42%, 66%, and 50%, respectively, and for a lead level of 1.21 μmol/L were 74%, 18%, and 97%, respectively. Receiver operating characteristic curves demonstrated that for detecting lead levels of 0.48 μmol/L with zinc protoporphyrin, the probability of a true-positive result is close to that of a false-positive one.
—Zinc protoporphyrin is not a reliable screening test for detecting low blood lead levels.(AJDC. 1993;147:66-68)