A federal advisory panel recently endorsed lowering the threshold for lead poisoning in young children, and eliminating the term "blood lead level of concern." If adopted, the recommendations would classify about 200,000 more children as having elevated lead levels, and could spell changes for lab test result reporting and quality assurance practices.
The Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) in January issued the recommendations, and the Centers for Disease Control and Prevention (CDC) is expected to act on them within 90 days.
The panel's recommendations reflect evidence available since 2003, the latest date included in a prior review. Based on this literature, ACCLPP is now recommending that "blood lead level of concern" be stricken from all future CDC policies, guidance documents, and other publications, and that public health efforts focus instead on primary prevention of lead exposure.
The panel noted that thresholds for blood lead levels requiring intervention in young children have been steadily lowered through the decades, from 60 µg/dL to 10 µg/dL. However, evidence has continued to mount that even small amounts of lead can be harmful. In addition to IQ deficits, the panel noted an array of adverse health effects in children associated with blood lead levels <10 µg/dL, including cardiovascular, immunological and endocrine issues, findings that cross socioeconomic lines. "It is now clear that there is no known threshold below which adverse effects of lead are absent," the panel wrote. Separately, a National Toxicology Program monograph issued in October 2011 found sufficient evidence for adverse health effects in children and adults at blood lead levels <10 µg/dL and <5 µg/dL.
The panel also proposed a new reference value of 5 µg/dL—based on the 97.5th percentile of National Health and Nutrition Examination Survey data— to identify children ages 1–5 with elevated blood lead levels. ACCLPP advised that CDC update this value every 4 years based on the latest population-based data.
Gwendolyn McMillin, PhD, co-chair of AACC's Therapeutic Drug Monitoring and Toxicology Division, hailed the recommendations as long overdue. "Many laboratories and individual states have already implemented the lower reference interval of 5 µg/dL for lead poisoning. Standardizing, once again, across the nation will certainly help improve detection and management of lead poisoning." McMillin is medical director of clinical drug abuse and trace element testing at ARUP Laboratories and associate professor of pathology at the University of Utah in Salt Lake City.
The panel suggested that labs and other providers offer simple information about the meaning of elevated blood lead level test results, defining terms like detectible level or elevated blood lead level. "Test results should not be mysterious or difficult to obtain," the committee wrote.
ACCLPP proposed a new management algorithm for clinicians, along with age- and blood lead level-specific thresholds for screening, repeat testing, and other interventions. Capillary blood lead tests above the reference value should be repeated, with the value of the screening test determining how quickly the confirmatory test result will be needed.
The panel reiterated a previous recommendation to lower the allowable laboratory error in blood lead level proficiency testing programs to ±2 µg/dL from ±4 µg/dL for blood lead levels <20 µg/dL. A laboratory work group of the ACCLPP is continuing to examine this issue, according to the ACCLPP chair, George Rhoads, MD, MPH. This group "has been actively engaged in assessing the extent to which the nation's clinical laboratories can be expected to tighten the error range for blood lead determinations without unreasonably increasing costs," he said. "Clearly, the old ±4 µg/dL standard is too broad to serve well if a level as low as 5 µg/dL is accepted as an action level. However, it is likely to take some months for the work group to address this issue and the ACCLPP itself is not expected to meet again to hear a report from the work group until late this year. Fortunately, most laboratories are believed to have error ranges that are significantly narrower than ±4 µg/dL, but laboratory variation can be expected to be a practical issue in implementing an action level of 5 µg/dL." Rhoads is the interim dean and professor of the UMDNJ School of Public Health in Piscataway, N.J.
McMillin was less confident about how easily labs would meet the proposed proficiency testing parameters. "Tightening the expectations for testing error to ±2 μg/dL may be a challenge for laboratories, and improvements in assay methodologies are likely to be required," she observed.
According to Rhoads, CDC has not yet indicated what actions it will take in response to the recommendations.