Test Catalog

Test ID: PBDV    
Lead, Venous, with Demographics, Blood

Useful For Suggests clinical disorders or settings where the test may be helpful

Detecting lead toxicity

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Lead is a heavy metal that is naturally found in the environment that can be an acute and chronic toxin. Lead can enter the environment through releases from mining lead and other metals, and from factories that make or use lead, lead alloys, or lead compounds. Lead is released into the air during burning coal, oil, or waste. Before the use of leaded gasoline in motor vehicles was banned (January 1, 1996), most of the lead released into the U.S. environment came from vehicle exhaust.

 

Lead was banned from household paints in 1978, but is still found in paint produced for nondomestic use and in artistic pigments. Ceramic products available from noncommercial suppliers (such as local artists) often contain significant amounts of lead that can be leached from the ceramic by weak acids such as vinegar and fruit juices. Lead is commonly found in soil especially near roadways, older houses, old orchards, mining areas, industrial sites, near power plants, incinerators, landfills, and hazardous waste sites. Recent data has also shown that inexpensive cosmetic jewelry pieces sold to the general public may contain high levels of lead which can be transferred to the skin through routine handling. However, not much lead can get into your body through your skin.

 

People may be exposed to lead by eating food or drinking water that contains lead. Drinking water in houses containing lead pipes may contain lead, especially if the water is acidic or "soft". Foods may contain small amounts of lead. Leafy fresh vegetables grown in lead-containing soils may have lead-containing dust on them. Lead may also enter foods if they are put into improperly glazed pottery or ceramic dishes and from leaded-crystal glassware. However, since lead solder is no longer used in cans, very little lead is typically found in food.

 

The typical diet in the United States contributes 1 to 3 mcg of lead per day, of which 1% to 10% is absorbed; children may absorb as much as 50% of the dietary intake, and the fraction of lead absorbed is enhanced by nutritional deficiency. The majority of the daily intake is excreted in the stool after direct passage through the gastrointestinal tract. While a significant fraction of the absorbed lead is incorporated into bone (approximately 94% adults; approximately 73% children) and erythrocytes, lead ultimately distributes among all tissues, with lipid-dense tissues such as the central nervous system being particularly sensitive to organic forms of lead. All absorbed lead is ultimately excreted in the bile or urine. Soft-tissue turnover of lead occurs within approximately 120 days.

 

Other alternative sources of lead include: moonshine distilled in lead pipes, some traditional home medicines, non-Western cosmetics (eg, surma and kohl), and some types of hair colorants, cosmetics, and dyes.

 

Lead expresses its toxicity by several mechanisms: 1) it avidly inhibits delta-aminolevulinic acid dehydratase and ferrochelatase, two of the enzymes involved in the synthesis of heme. In the end, this inhibition causes decreased hemoglobin synthesis resulting in anemia. 2) Lead is also an electrophile that avidly forms covalent bonds with the sulfhydryl group of cysteine in proteins. Thus, proteins in all tissues exposed to lead will have lead bound to them. The most common sites affected are epithelial cells of the gastrointestinal tract and epithelial cells of the proximal tubule of the kidney.

 

Avoidance of exposure to lead is the treatment of choice. However, chelation therapy is available to treat severe disease and may be necessary especially in children if the blood lead is higher than 45 mcg/dL. The standard chelating agents currently in use are dimercaprol (British Anti-Lewisite, or BAL), CaNa2-EDTA (or EDTA), penicillamine, and 2,3-dimercaptosuccinic acid (DMSA; Succimer).

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

All ages: 0.0-4.9 mcg/dL

Critical values

Pediatrics (< or =15 years): > or =20.0 mcg/dL

Adults (> or =16 years): > or =70.0 mcg/dL

Interpretation Provides information to assist in interpretation of the test results

No safe blood lead level in children has been identified. Lead exposure can affect nearly every system in the body. Because lead exposure often occurs with no obvious symptoms, it frequently goes unrecognized. The current reference level at which CDC recommends public health actions be initiated is 5 mcg/dL. Chelation therapy is generally indicated in children when whole blood lead concentrations are above 45 mcg/dL .

 

The Occupational Safety and Health Administration (OSHA) has published the following standards for employees working in industry. The OSHA Standards for General Industry (CFR 1910.1025) and Construction (CFR 1926.62) applies to workers exposed to airborne lead levels 30?mcg/m(3) or greater time-weighted average and requires the removal of workers if a periodic and follow-up blood lead level is 60?mcg/dL (2.9?mcmol/L) or greater, 50?mcg/dL (2.4?mcmol/L) or greater for construction, or the average blood lead level of all tests over a 6-month period (or if there are fewer than three tests over a 6-month period, the average of three consecutive tests) is 50?mcg/dL (2.4?mcmol/L) or greater. Workers with a single blood lead level meeting the numerical criteria for medical removal must have their blood lead level retested within 2 weeks. If a worker is medically removed, a new blood lead level must be measured monthly during the removal period. Workers are permitted to return to work when their blood lead level is 40?mcg/dL (1.9?mcmol/L) or less. According to the OSHA Lead Standards, a zinc protoporphyrin (ZPP) is also required on each occasion a blood lead level measurement is made.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. www.cdc.gov/exposurereport

2. www.atsdr.cdc.gov/ToxProfiles/tp13.pdf

3. de Burbure C, Buchet J-P, Leroyer A, et al: Renal and neurologic effects of cadmium, lead, mercury, and arsenic in children: evidence of early effects and multiple interactions at environmental exposure levels. Environ Health Perspect 2006;114:584-590

4. Kosnett MJ, Wedeen RP, Rothenberg SJ, et al: Recommendations for medical management of adult lead exposure. Environ Health Perspect 2007;115:463-471

5. Jusko T, Henderson C, Lanphear B, et al: Blood lead concentrations <10 mcg/dL and child intelligence at 6 years of age. Environ Health Perspect 2008;116:243-248

6. Nader R., Horwath AR., Wittwer CT: Chapter 42: Toxic Elements. In Tietz Textbook of Clinical Chemistry and Molecular Diagnostics Sixth Edition. St. Louis, Elsevier, 2017, pp 907-910

Special Instructions Library of PDFs including pertinent information and forms related to the test