Delta-aminolevulinic acid dehydratase and zinc protoporphyrin in very low lead-exposed pets: a community study

Markers of lead intoxication have been developed based on their capacity to identify lead intoxication at the preclinical, ie biochemical stage of manifestation. However, little information on these markers is available under conditions of low lead exposure. This prompted us to conduct a community-based study to determine the usefulness of theta-aminolevulinic acid dehydratase (ALAD) and zinc protoporphyrin (ZnPP) in conditions of low lead environmental exposure by studying the relationships between low blood lead levels, ALAD and ZnPP in a large group of healthy dogs living in an Italian urban area. The study population consisted of 79 dogs. Each sample was tested for ALAD, lead and ZnPP and for complete blood count, hemoglobin, AST, ALT, and urea values. A weak inverse relationship between ALAD and ZnPP was found. An inverse relationship between ALAD and lead concentrations was found in the whole group (p < 0.0005). This relationship remained significant when selecting the values falling between 2 standard deviations of the mean blood lead concentrations of the population below the "concerned lead levels" (< 10 mg/dl; p = 0.0005). There was no relationship between whole blood ZnPP concentrations and whole blood lead levels. The sensitivity and specificity of ALAD measurements, calculated by using the 2 x 2 contingency table with respect to blood lead concentrations, were of poor predictive diagnostic value.