July 26, 2017
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Low blood lead levels difficult to detect in children

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The blood lead levels of children between the ages of 1 and 5 years has decreased to a point where laboratories across the United States are having a difficult time detecting the trace amounts, according to a study published in Pediatrics.

“In 2012, the CDC’s Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) recommended using a population-based reference value, calculated as the 97.5th percentile of blood lead in children 1 to 5 years old in the U.S. instead of a blood lead ‘level of concern’ to identify children and environments associated with lead hazards,” Kathleen L. Caldwell, PhD, from the division of laboratory sciences at the CDC, and colleagues wrote.

The researchers note that the CDC has recommended an update to the reference value every 4 years, which is to be based upon the most current National Health and Nutrition Examination Survey (NHANES) blood lead data for this demographic.

To update this reference value, the researchers used the CDC’s NHANES, a complex, multistage, probability cluster sample that was created to be nationally representative. The survey is based on age, sex and race/ethnicity, and has been occurring every year since 1999. Approximately 5,000 American citizens who are noninstitutionalized had their health and nutritional status assessed through interviews, surveys, physical examinations and clinical specimens for the survey.

More “failures” were noted between 2009 and 2016 due to the CDC’s decreased limits of detection of lead in whole blood and the decreased blood lead levels in the U.S. population. For the time during which this study was conducted, 359 manufacturing lots were screened by the lab, including needles, blood collection tubes, cryovials and other items, for lead levels. The number of screening failures in children 1 to 5 years is indicative of lessened blood lead levels.

Those with significant blood lead levels of 3.48 µg/dL or more were more likely to be part of a household whose annual income is under $20,000 (P ­= 0.006) and the child is younger 3 years of age (P = 0.04). Other risk factors included being non-Hispanic black and male.

The researchers note that the 66 labs that were included in the study did an acceptable job at all blood lead level concentrations. In 40% of cases with low blood lead levels, they were labeled as below the limit of detection, and less than or equal to 60% reported actual values when levels were at 1.48 µg/dL or less.

“When a child is retested [for blood lead levels], any result between 0 and 8 µg/dL includes the possibility that the true blood lead level is unchanged,” Caldwell and colleagues wrote.” “It would be helpful for the clinician to explain to a parent or guardian the concept of variability in the measurement if, for example, a child’s blood lead level goes from 4 to 8 µg/dL in the absence of a new or increased exposure.”— by Katherine Bortz

Disclosure: The researchers provide no relevant financial disclosures.