The Centers for Disease Control and Prevention (CDC) provides regulations and guidance for interpretation of blood lead testing in children in the United States. This includes providing a blood lead level (BLL) value above which action should be taken. An update to the blood lead reference value (BLRV) was published on October 27, 2021, that lowered the BLRV from 5.0 µg/dL to 3.5 µg/dL (MMWR Morb Mortal Wkly Rep 2021;70:1509-12).
The BLRV is generated from population-based data gathered from children 1−5 years old who were part of the National Health and Nutrition Examination Survey (NHANES) and reflects the 97.5th percentile of this group. NHANES is a nationwide survey that assesses the health and nutritional status of a population representative of the United States. As such, the BLRV is not a reference interval and is definitely not a “normal range.” Rather, the BLRV acts to guide medical follow-up for individuals, as well as to identify communities with the greatest need for lead remediation, or primary prevention efforts.
In fact, CDC clearly states that there is no safe level of blood lead, as even very small amounts of lead can be detrimental to brain development. And eventually, we may see the BLRV decrease even further. Historically, the threshold for interpreting BLL in children has changed significantly: in the 1960s, 60 µg/dL was considered noteworthy, and as clinical and scientific evidence evolved, the threshold dropped.
In addition to the updated BLRV, guidance for confirmation of and follow-up on elevated BLLs was updated. The revised guidelines, titled “Recommended Actions Based on Blood Lead Level,” can be found at www.cdc.gov.
What are the laboratory standards for blood lead testing?
The CLIA analytical quality requirements for blood lead testing are ±10% or ±4 µg/dL, whichever is greater. Unfortunately, this is a fairly wide range, especially when a clinically significant value is 3.5 µg/dL.
How should samples be collected for BLL testing?
Whole blood samples for BLL analysis may be collected from either capillary or venous sources. To prevent contamination, collection areas and equipment should be lead-free or thoroughly cleaned with lead-free wipes. For capillary collection, wash the patient’s hands with soap and water and allow them to air dry without touching anything. If additional tests are collected at the same time, tubes for lead testing should be collected first.
Samples collected by capillary puncture are more prone to contamination. Therefore, capillary samples with BLLs over the BLRV need to be confirmed with a venipuncture sample.
Who should have their lead levels tested?
Each state has specific requirements for testing. In addition, the Centers for Medicare and Medicaid Services require that all Medicaid-enrolled children be tested at 12 and 24 months of age, or at 24−72 months if they were not screened earlier.
Pregnant individuals who are at high risk for lead exposure may be screened at the discretion of their physician. Testing for workplace exposure is managed by the Occupational Safety and Health Administration.
What’s going on with the LeadCare testing system?
The Magellan LeadCare analyzers are small devices that measure BLLs based on anodic stripping voltammetry. Due to their small sizes and, in some cases, CLIA-waived status, these devices are often used in office and point-of-care settings. Some laboratories with low testing volumes may also use LeadCare analyzers. In the last 5 years, however, there have been multiple notifications about recalls affecting the use of these devices. Currently, these analyzers can still be used, so long as non-recalled lots of reagent and quality control are used, and only capillary samples are tested.
Amy L. Pyle-Eilola, PhD, DABCC, FACB, is the director of clinical chemistry at Nationwide Children’s Hospital in Columbus, Ohio. +Email: [email protected]