according to a recommendation from the U.S. Preventive Services Task Force.
Elevated blood lead levels are associated with potentially irreversible neurologic problems in children and with organ system impairment and adverse perinatal effects in pregnant women, according to the statement.
“Thus, the primary benefit of screening may be in preventing future exposures or exposure of others to environmental sources,” the task force members wrote in.
However, the task force issued I statements, meaning that “the current evidence is insufficient to assess the balance of benefits and harms of screening for elevated blood lead levels” in asymptomatic children aged 5 years and younger and in asymptomatic pregnant women.
The task force cited evidence that questionnaires and other clinical prediction tools are inaccurate at identifying elevated blood lead levels in asymptomatic children and pregnant women. In addition, the task force found adequate evidence that capillary blood testing identified elevated blood lead levels in children, but found inadequate evidence that treating elevated blood lead levels was effective in asymptomatic children aged 5 years and younger or in pregnant women.
In the evidence report accompanying the recommendation statement in, , of Oregon Health & Science University, Portland, and her colleagues reviewed data from a total of 24 studies including 11,433 individuals.
None of the studies evaluated the risks or benefits of blood lead screening in children. However, in three of four studies, capillary blood lead testing showed sensitivities ranging from 87% to 91% and specificities from 92% to 99%, based on a blood lead level cutoff of 10 mcg/dL or less.
“Evidence indicates that capillary sampling is slightly less sensitive than venous sampling, with comparable specificity,” Dr. Cantor and her colleagues wrote. “Both methods require confirmation.”
There is only limited evidence on whether intervening when children present with elevated blood lead levels results in better neurodevelopmental outcomes. One trial showed beneficial effects of dimercaptosuccinic acid chelation of lowering elevated blood lead levels (20-44 mcg/dL) at 1 year versus placebo, but no clear effect on longer term blood lead levels or neurodevelopmental outcomes, they reported.
For residential interventions, again evidence is limited and blood lead concentrations were not clearly affected. Evidence on calcium and iron interventions was poor quality and insufficient to tell if there was an effect on blood lead levels or clinical outcomes, Dr. Cantor and her colleagues wrote.
No studies of screening for elevated lead levels in pregnant women were identified, nor were studies of health outcomes after interventions to reduce blood lead levels in asymptomatic pregnant women, they noted.
Studies involving pregnant women were limited, and included data on the diagnostic accuracy of a clinical questionnaire and the effects of nutritional intervention during pregnancy, Dr. Cantor and her colleagues wrote.
“This update confirms there are no clear effects of interventions for lowering elevated blood levels in affected children or to improve neurodevelopmental outcomes,” they concluded. “Evidence to determine benefits and harms of screening or treating elevated lead levels during pregnancy remains extremely limited.”
The recommendation updates the last version issued in 2006. The USPSTF is supported by the Agency for Healthcare Research and Quality. The researchers for both articles reported no relevant financial disclosures.
SOURCE: Curry SJ et al. ; Cantor AG et al. .