δ-Aminolevulinic Acid Dehydratase Test for Lead Exposure

The determination of δ-aminolevulinic acid dehydratase (ALA-D) in erythrocytes is one of the most reliable indicators for evaluating occupational exposure to a low concentration of lead. The ALA-D test is usually performed with incubation at the pH level found in normal blood. However, the optimum pH for determinations of ALA-D in occupational lead exposure is different from, and at a lower pH level compared with, the normal. Accordingly, I undertook to perform the ALA-D assay by simultaneous incubation at the normal and at a lower pH value, and the results were expressed as the value of an activity ratio in addition to the activity. The activity ratio in the ALA-D test has a close correlation with the level of lead in blood.