Evaluation of Erythrocyte Protoporphyrin and Zinc Protoporphyrin as Micro Screening Procedures for Lead Poisoning Detection

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Abstract
Seven hundred and three blood samples from children were analysed for lead by Delves cup atomic absorption, for protoporphyrin by solvent extraction and fluorescence, and for zinc protoporphyrin with two manufacturers' models of an automated front-face fluorimeter (haematofluorimeter). The power of protoporphyrin analysis for predicting the level of lead in blood was found to be poor. Up to 30% of children with lead concentrations of ≥40 g/100 ml (≥1·93 μmol/l) and nearly 60% of children with ≥30 μg/100 ml (≥1·45 μmol/l) would remain undetected if protoporphyrin analysis were used for screening with an action level of 60 μg/100 ml (1·07 μmol/l) for the porphyrin analysis. The predictive power of protoporphyrin analyses improves with the age of the child, indicating that the less expensive protoporphyrin test may be acceptable for older children, if by this means a large population of children at risk can be screened.