New saliva lead test - using oral fluid for lead screening: Combating lead poisoning in our children, communities, and ourselves

By Erica A. Guice, Western Slope Laboratory, LLC

Lead has been demonstrated to be harmful to most living things. It is very detrimental to human beings, even at very low levels. As such, efforts have been made to remove lead from common products such as paint, gasoline, plumbing pipes, and food cans. Consequently, acute lead poisoning is now rare in the developed world. Nevertheless, chronic exposure to lead through hobbies, occupation, and the environment does still occur. This exposure is quite dangerous leading to neurodevelopmental and profound IQ deficits in children and elevated blood pressure, kidney problems, and infertility in adults.

Due to these harmful effects, lead concentrations are monitored, generally at the local level, following standardized guidelines. The Centers for Disease Control and Prevention (CDC) has stated that childhood lead poisoning is the number one environmental health risk facing children in industrialized countries today. One out of six children, which is more than three million children age six and younger, have toxic levels of lead in their bodies in the United States alone. However, adult lead poisoning rates are at the level of six persons per every 100,000, which is down 14% from 2004. With the number of persons afflicted with toxic lead levels, the CDC has recently reduced the action level for whole blood to 5µg/dL in children; the elevated lead level for adults is 10µg/dL.

Since most clinical laboratories rely on atomic absorption (AA) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) to test whole blood as a screen, the implementation of testing to detect even lower action levels will probably not be addressed due to the limitations of these technologies. In an effort to utilize more sensitive technology and reduce, if not eliminate, the need for painful, invasive blood testing, Coventry Diagnostics, LLC began research into a salivary lead test. This test employs inductively coupled plasma mass spectrometry (ICP-MS) and therefore has increased sensitivity which allows for lower levels to be detected. In the first study in 2005, with Guilford County Department of Public Health (North Carolina, United States), Dr. David R. Schneider was able to demonstrate the utility of using oral fluid for lead screening while overcoming many of the obstacles named by previous researchers in the field. The study demonstrated an equivalent correlation between salivary lead and whole blood lead. Paired sets of the data are shown below in Graph One. As demonstrated in Graph Two, the distribution of concentration was the same and the mean values were the same. This result was statistically significant. Continued studies looking at lead levels above the CDC action level has been undertaken, first in Texas (US) and now in the UK. These subsequent studies are also including the comparison with plasma lead levels to aid in the detection of vulnerable fetuses.

Coventry Diagnostic, LLC was issued a US patent for the Schneider method of salivary lead testing with ICP-MS. The method allows for the detection of lead in oral fluid with levels as low as 0.05µg/dL; this is one hundred times lower than the current CDC action level for children. The patented method has an accuracy greater than 94% for the major lead isotopes (206, 207, and 208) while maintaining extreme precision. The overall uncertainty of the method is no more than 1% for each isotope.

The impact of a noninvasive, salivary lead screening test will allow for more testing and will lead to faster adaptation of the method. Currently, the test is available on a limited basis to the construction and demolition industry in the UK via a distributor. Persons can also purchase the test directly from Western Slope Laboratory, LLC, a wholly-owned subsidiary of Coventry Diagnostics, LLC. The test is available worldwide, but all testing is performed at the Troy, MI, United States facility of Western Slope. Anyone, not just physicians and other medical practitioners, can use the Coventry salivary lead test since it is designed to be user friendly. The test is very economical since it does not require a trip to a physician’s office; the cost is $80 (AUD) and the donor must cover shipping. Western Slope recommends postal couriers or a logistical shipping company like Federal Express (FedEx). Results are released via an online reporting network within seven business days of receipt of sample. Purchasing and shipping costs can vary with number and weight of the packages.

Due to the aforementioned correlative data, the suggested action level for oral fluid is the same as whole blood screening. As such, Western Slope Laboratory suggests that donors with levels above 5µg/dL in children and 10µg/dL in adults consult their physicians if in the United States. It is suggested that donors in other countries follow their respective health department guidelines. In consulting their guidelines, please note that the correlation is such that values under 10µg/dL were corresponding.

At this time, Western Slope Laboratory is also investigating this method for use in testing for other heavy metals including aluminum, mercury, arsenic, copper, and uranium. For more information on lead or any other metal testing in oral fluid, please contact Western slope Laboratory 0011+1-800-789-4317 x 22.

Graph One:

Graph Two:

References

Klaassen, Curtis D. Casarett and Doull’s Toxicology: The Basic Science of Poisons. New York: McGraw-Hill 1996 5th Edition

Canfield et al (2003) Intellectual Impairment in Children with Blood Lead Concentrations below 10µg per Deciliter The New England Journal of Medicine 348(16):1517-26

Department of Health and Human Services Centers for Disease Control and Prevention National Center for Environmental Health www.cdc.gov/nceh/lead

Barbosa F Jr et al (2005) A critical review of biomarkers used for monitoring human exposure to lead: advantages, limitations, and future needs Environmental Health Perspective 113(12):1669-74

Stobbe, M (2011) Lead poisoning in adults is down, CDC reports say The Bellingham Herald 6/30/2011