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Article |

Use of Zinc Protoporphyrin Measured by the Protofluor-Z Hematofluorometer in Screening Children for Elevated Blood Lead Levels

Phillip B. Rolfe, MD; John F. Marcinak, MD; Allen J. Nice, MS, MT; Robert H. Williams, PhD
Am J Dis Child. 1993;147(1):66-68. doi:10.1001/archpedi.1993.02160250068020.
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• Objective.  —To determine the usefulness of zinc protoporphyrin, as measured by the Helena Protofluor-Z hematofluorometer, for detecting elevated lead levels.

Design.  —Observational, descriptive review of laboratory records from a university toxicology laboratory.

Setting.  —Inner-city university pediatric clinic and two affiliated community clinics in Chicago, Ill.

Patients.  —Seven hundred seventy-five children younger than 7 years with paired lead-zinc protoporphyrin results.

Measurements/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.

Conclusion.  —Zinc protoporphyrin is not a reliable screening test for detecting low blood lead levels.(AJDC. 1993;147:66-68)


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