Lead testing: the changes and challenges

Lead poisoning continues to be a significant problem affecting the health and development of children in significant numbers. According to a recent National Health and Nutrition Examination Survey (NHANES), approximately 535,000 U.S. children ages one through five have elevated levels of lead in their blood.¹ The Centers for Disease Control and Prevention (CDC) describes the impact of lead: “Low levels of lead in blood have been shown to affect IQ, ability to pay attention, and academic achievement. And effects of lead exposure cannot be corrected.”²

Lead exposure is often asymptomatic, or it may present with vague symptoms such as headache, fever and chills. A blood test is the only way to determine if lead exposure has occurred.

Recent CDC changes

In May 2012, the CDC responded to the growing number of research studies concluding that there is no safe level of lead and changed its definition of an elevated blood lead level (BLL). Previously, a BLL of 10 µg/dL was considered to be the “level of concern.” The CDC abandoned the use of the 10 µg/dL level of concern in favor of a new blood lead “reference value” of 5 µg/dL, representing the 97.5th percentile of blood lead distribution in U.S. children.²

The impact on clinical laboratories

As a result of the lower reference value, it is likely that a greater number of children will be identified as having been exposed to lead. Preventive screenings at ages 12 and 24 months are essential to identifying childhood lead exposure and to helping parents and physicians to take earlier action to reduce this exposure. The new reference value will also impact the physicians and laboratories responsible for performing blood lead testing, increasing the need for accurate, reliable, and cost-effective testing methods.

Current testing methods

There are a number of methodologies available for blood lead testing including clinical laboratory instruments and point-of-care analyzers. These methods, presented in Table 1, offer differing levels of complexity, from required equipment to laboratory training, and the choice of method will impact laboratory workflow, throughput, and time-to-result:

• Inductively coupled plasma mass spectrometry (ICP-MS)

• Graphite furnace atomic absorption spectrometry (GFAAS)

• Anodic stripping voltammetry (ASV)—Clinical

• Anodic stripping voltammetry (ASV)—Point-of-Care (POC)

Table 1. Blood lead testing methods

 
One future concern for physicians and laboratories is that the blood lead reference value will be evaluated every four years by the CDC, based on the most recent NHANES data. The impact of this re-evaluation is unknown, but it raises at least two important questions: Will laboratories be able to meet the demands for increased testing (staffing, time, cost)? How will the available analytical methods continue to meet the level of detection required if the reference value is lowered?

The general recognition that there is no safe level of lead will have a positive impact on the health of children. Laboratories and testing methodologies will continue to evolve to provide the diagnostic tools needed to achieve the goal of eliminating childhood lead poisoning.