Nearly half of children who have elevated levels of lead in their blood are not re-tested as recommended, according to new study findings released Tuesday.

Lead is a neurotoxin that has been blamed for a variety of learning problems in children.

Experts suggest that all children with high levels of lead in their blood be tested again within 3 months to confirm that the initial reading is correct, make sure their lead levels don’t continue to rise, and check if any interventions are working.

“Follow-up testing is the cornerstone of management for children with elevated blood lead levels,” told Ann Arbor, study author Dr. Alex R. Kemper at the University of Michigan, .

More than half of the children who were not re-tested had at least one visit with a healthcare worker, meaning there were many “missed opportunities” for children to be re-screened, Kemper noted.

Just why so many children are not followed up properly is unclear, Kemper said. In many cases, parents may feel like “there’s not much they can do,” he said, or may simply have never been told their children had elevated levels of lead in their blood.

All of the nearly 4,000 children included in the survey were covered by Medicaid, the government’s low-income health plan. Research shows that children enrolled in Medicaid have a three-fold higher risk of lead poisoning, Kemper noted, likely because lower-income families often live in older homes, which contain more lead.

Most lead poisoning occurs because children ingest chips or dust from lead-based paint. Though federal law now strictly limits lead levels in residential interior paint, millions of American homes are believed to still have surfaces painted with older, more dangerous paint.

For their study, Kemper and his team reviewed information collected from 3,682 children 6 years old or younger for whom routine screening showed they had elevated levels of lead in their blood.

Only 54 percent of children with lead poisoning were re-tested within 6 months, the authors report in the Journal of the American Medical Association. Children were less likely to be retested if they were not white, lived in urban areas, and resided in regions where children commonly develop lead poisoning.

In an interview, Kemper noted that it’s not clear why children living in high-risk areas were less likely to be re-tested. It’s possible that in areas where it’s uncommon, finding a child with high blood lead levels may “set off alarms,” and healthcare workers follow them more diligently, he said.

“We hope that our study raises awareness about lead poisoning and leads to the development of policies that protect all children,” Kemper noted.

In an accompanying editorial, Dr. Bruce P. Lanphear of the Cincinnati Children’s Hospital Medical Center in Ohio writes that healthcare workers need to screen and re-test at-risk children, but the “focus” of public health efforts should be on keeping kids safe from lead in the first place.

“The key to primary prevention is to require screening of high-risk, older housing units to identify lead hazards before a child is poisoned,” he writes.

Lanphear served as an expert witness in a suit against the lead industry, on behalf of Milwaukee.

SOURCE: Journal of the American Medical Association, May 11, 2005.