The free erythrocyte protoporphyrin assay in monitoring lead-exposed workers. Comparison of two fluorometric methods.

We have performed a comparative analysis of two different fluorometric methods used to determine free erythrocyte protoporphyrin (FEP) blood concentration. The first method is based on an extractive procedure, whereas the second one involves the direct fluorometric analysis of whole blood. Our results show that the extractive procedure is probably the most reliable technique available for FEP determination, but it is not so suitable for mass screening, whereas the direct fluorometric determination of FEP blood concentration is probably less reliable, but sufficiently enough to be used for mass screening. We have furthermore investigated whether the FEP test could be used as a unique monitoring method for subclinical lead poisoning. Our findings indicate that FEP test can detect very early metabolic alterations, but it is not so suitable for determining lead absorption and should therefore be used in mass screening together with a dose indicator, such as blood lead concentration.