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Mechanism of delta-aminolevulinic acid (ALA) accumulation in lead poisoning. Mass Screening `Practical' Lead Poisoning Test Simple, Rapid A simplified laboratory procedure, using piggy-back disposable chroma tographic columns, may permit mass screening of ghetto children and in dustrial workers exposed to lead poisoning. Last summer, use of the method in a random survey of some 3,500 Chicago children led Loyola clini cians to estimate that over 14,750 children had abnormal lead expo sure in that city alone. Instead of the conventional 5 to 10 ml of blood required in other tests, 0.5 ml urine samples are used in the test developed by Joseph R. Davis, MD, PhD, and colleagues. A single technician can conduct 200 measurements within five hours, he told an Atlantic City audience. A modification of previous, more cumbersome methods, the new test measures urinary concentration of delta-aminolevulinic acid (ALA) -- instead of lead itself. In 1960, Scan dinavian workers established that ALA, an intermediate product in porphyrin biosynthesis, is increased with abnormal lead exposure. Re cent evidence indicates this is be cause the enzyme, ALA dehydrase, is blocked by lead. Radi summer, heat and other fac tors precipitate serious illness and death in children who may have con sumed lead months before, said Dr. Davis, associate professor of phar macology, Loyola University Stritch School of Medicine. Because many potential victims are asymptomatic, rapid, inexpen sive and accurate screening proce dures are necessary, he said. Experi ence with over 10,000 urinary ALA ently well, asymptomatic children." determinations show the test is re The test appears equally applica liable. ble in adults. Among groups now be In an early study of 250 children ing evaluated are 300 workers at a with suspected lead poisoning, an Naval ordnance plant. ALA concentration of 1.00 mg/100 "Urine samples are frozen np to ml was established as the upper limit I ten hours after collection. In this of normal. Fewer than 5% of those \ way stored samples retain stable with ALA levels below this bench \ALA levels for many months. mark required chelation therapy be ' The Chicago test originally de cause of clinical symptoms. But over pended on plunger-less syringes 65% of children with urinary ALA suitably packed to become small exceeding 1.00 mg/100 ml required chromatography columns. A dispos therapy. able plastic unit in kit form is now Further single-blind studies indi available commercially. cated that urinary ALA results cor The newer units contain two small relate with serum concentrates and columns mounted piggy-back. The clinical criteria in 91% of cases. Of tube on top contains an anionic ex the remainder about 6% are false change resin which filters porphobi positive, 3% false-negative. linogen from the urine. The bottom Last summer, a Loyola-Chicago column, with a cationic exchange Board of Health team conducted a resin, captures ALA while allowing random sample of children ages 1 to urea and other substances to pass 7 years in "high-risk" predominant through. ly ghetto areas. Among the 3,500 The 10-step procedure concludes children who contributed urine sam with a heat condensation reaction to ples to mobile collecting units, 5.9% form the ALA pyrrole and the addi had elevated ALA levels. Statistical tion of Ehrlich's reagent. Elevated projections would place the number ALA is marked by a reddish conden of abnormally-exposed Chicago chil sation, with normal values usually dren at about 14,750, he commented. faint yellow. Precise concentrations "This further emphasizes the need are calculated with the aid of a for such determinations in appar standard laboratory colorimeter. Printed m u .s .a . DUP050312922