Lead

Test Overview

This test measures the amount of lead in the blood. Lead is a poisonous (toxic) metal that can damage the brain and other parts of the body. A lead blood test may be done on blood drawn from the vein, a finger (finger stick), or the heel (heel stick).

A person can be exposed to lead:

  • By eating or drinking lead-contaminated foods, water, or other material (such as paint chips).
  • By breathing dust or smoke containing lead.
  • Through skin contact with lead.

There is no safe age to be exposed to lead. Adults can have problems from lead poisoning, but it is most harmful to children younger than age 6 (especially those younger than age 3) because it can permanently affect their growth and development. A pregnant woman who is exposed to lead can pass it to her baby (fetus). Lead can also be passed to a baby through the mother's breast milk.

Why It Is Done

A lead blood test is done to:

  • Diagnose lead poisoning.
  • See how well treatment for lead poisoning is working.
  • Look for lead poisoning in people who work with lead or lead products or live in places where the chance of poisoning is high, such as in a large city.

How To Prepare

No special preparation is required before having this test.

Be sure to tell your doctor if you are using any herbal medicines.

How It Is Done

Blood tests for lead should be done by a lab experienced in proper technique.

Blood sample from a heel stick

For a heel stick blood sample, several drops of blood are collected from the heel of your baby. The skin of the heel is first cleaned with alcohol and then punctured with a small sterile lancet. Several drops of blood are collected in a small tube. When enough blood has been collected, a gauze pad or cotton ball is placed over the puncture site. Pressure is maintained on the puncture site briefly, and then a small bandage is usually applied.

A heel stick must be done carefully to prevent contamination of the sample from lead on the skin. If a heel stick blood sample comes back positive for lead, a sample of blood from your baby's vein will be tested to confirm the results.

Blood sample from a vein

The health professional taking a sample of your blood will:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then put on a bandage.

How It Feels

Blood sample from a heel stick

A brief pain, like a sting or a pinch, is usually felt when the lancet punctures the skin. Your baby may feel a little discomfort with the skin puncture.

Blood sample from a vein

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

Heel stick

There is very little chance of a problem from a heel stick. A small bruise may develop at the site.

Blood test

There is very little chance of a problem from having blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
  • Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

This test measures the amount of lead in the blood. Lead is a poisonous (toxic) metal that can damage the brain and other parts of the body.

Acceptable levels

Although it is not normal to have lead in your body, a small amount is present in most people. Values may vary from lab to lab. Results are usually available within 1 week.

Lead
Acceptable:

0–9 micrograms per deciliter (mcg/dL) or less than 0.48 micromoles per liter (mcmol/L)

If your blood test result is 10 mcg/dL or higher, your doctor will want you to have another blood test. How soon you will be retested is based on the results of your first test. If the result is only slightly high, you may be retested in a month. If it is very high, your doctor may want to repeat the test within a few days.

High levels

High levels of lead in the blood are caused by lead poisoning. There are five classes of lead poisoning, according to the United States Centers for Disease Control and Prevention (CDC). These levels range from class 1 (no lead poisoning, or less than 10 mcg/dL) to class 5 (a medical emergency of at least 70 mcg/dL).

Lead blood level classification
Class Blood lead level Effects in children

1

1–9 mcg/dL or less than 0.48 mcmol/L

Possible learning problems

2A

10–14 mcg/dL or 0.48–0.68 mcmol/L

Hearing problems, slowed growth, learning problems

2B

15–19 mcg/dL or 0.70–0.96 mcmol/L

3

20–44 mcg/dL or 0.97–2.1 mcmol/L

Headache, weight loss, nervous system problems

4

45–69 mcg/dL or 2.17–3.33 mcmol/L

Severe stomach cramps, poor production of red blood cells (anemia), seizures

5

More than 69 mcg/dL or more than 3.33 mcmol/L

Severe brain damage leading to death

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Contamination from the skin. Low levels of lead can be found almost anywhere, including on the skin.
  • Having low iron levels in your blood, which causes an increase in the absorption of lead.

What To Think About

  • Blood tests for lead should be done by a lab experienced in proper technique. A finger stick or heel stick can test for lead poisoning but must be done carefully to prevent contamination of the sample from lead on the skin. Any result of 10 mcg/dL of lead or higher from a finger or heel stick should be rechecked on a blood sample drawn from a vein. Some doctors prefer to only test blood drawn from a vein. If the results are too high, a follow-up blood sample should be taken from a vein to double-check the results.
  • Lead can also be measured in urine, although the amounts are normally very low. But if you are being treated for lead poisoning with medicine (chelation therapy), your urine may be tested to keep track of the amount of lead being removed from your body. Urine tests for lead are done on a sample of urine collected over a 24-hour period.
    • A lead mobilization test may be done to decide whether to treat lead poisoning with chelation therapy. For this test, calcium disodium versenate (calcium EDTA) is given intravenously or intramuscularly. Calcium EDTA binds to lead, causing it to be removed from body tissues then excreted in the urine.
    • A urine aminolevulinic acid (ALA) test may be done to check the extent of lead poisoning. ALA is a substance the body uses to make hemoglobin, the oxygen-carrying protein in red blood cells. In lead poisoning, the production of hemoglobin is blocked, causing ALA to build up in the blood and to be passed into the urine. Because urine ALA levels do not increase until blood lead levels are high, the urine ALA test is not a good way to test for lead poisoning in children.
  • The U.S. Occupational Safety and Health Administration (OSHA) requires companies to test the blood of employees who work with lead. Results need to be reported to the local health department if 2 or more blood lead levels are above 10 mcg/dL. A home inspection is needed to find the source of the lead. For more information, see OSHA's Web site at www.osha.gov.

References

Other Works Consulted

  • Committee on Environmental Health, American Academy of Pediatrics (2005). Lead exposure in children: Prevention, detection, and management. Pediatrics, 116: 1036–1046. Also available online: http://www.pediatrics.org/cgi/content/full/116/4/1036.
  • Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Occupational Safety and Health Administration, U.S. Department of Labor (2007). Safety and health topics. Lead. Available online: http://www.osha.gov/SLTC/lead.

Credits

Author Debby Golonka, MPH
Editor Susan Van Houten, RN, BSN, MBA
Associate Editor Tracy Landauer
Primary Medical Reviewer Michael J. Sexton, MD - Pediatrics
Specialist Medical Reviewer R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care, Medical Toxicology
Last Updated June 26, 2008

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