The lead test is used to evaluate the concentration of lead in the blood at the time the sample was collected. The blood lead test is used to screen for exposure to harmful levels of lead. It may also be ordered to monitor the effectiveness of treatment and to confirm that lead levels are decreasing over time.
Lead concentrations are monitored at the local level following state and national standards. The Centers for Disease Control and Prevention (CDC), the American Academy of Pediatrics (AAP), and a variety of other organizations make recommendations regarding screening children for lead exposure. Testing recommendations and the definition of what is an abnormal blood lead level have changed significantly over the past 45 years. In 1991, the CDC concluded that previous levels were not low enough, and in 1997 the blood lead level of concern for children was decreased from 25 micrograms per deciliter (mcg/dL) to 10 mcg/dL. In 2012, the CDC's Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) recommended lowering the blood lead level threshold to 5 mcg/dL, which the CDC accepted in May 2012.
Blood lead is monitored in workers whose environment contains lead. It is used to evaluate chronic lead exposure and recent lead exposure. Sometimes, a zinc protoporphyrin (ZPP) test is also ordered. The ZPP is increased when lead begins to affect red blood cell production. It is not sensitive enough to use as a screening tool for children, but it may be ordered to help evaluate average lead exposure in adults over the last several weeks.
For screening children: The CDC recommends that each state develop a plan to detect children who may have been exposed to lead. The AAP recommends that, at a minimum, screening be offered to:
Every Medicaid-eligible child at age 1 and again at 2 years of age
For children not eligible for Medicaid, AAP also recommends following any local recommendations for screening and, if there are none, health care providers should consider screening all children at least once at age 2 and preferably also at age 1, unless lead exposure can be confidently excluded.
People should check with their local health department regarding lead screening guidelines specific to the risks in their area.
The CDC and AAP also recommend that health care providers and state screening programs consider screening children of parents who work with lead as well as immigrant, refugee, and other foreign-born children of any age when they enter the United States.
Managing children with elevated blood levels: Since fingerstick samples can be contaminated during collection of the specimen, an initial elevated result obtained by a fingerstick sample should be repeated with a venous test for confirmation, usually within a week to a month after the first test. Follow-up testing is then used to monitor the persistence of an elevated blood lead test and is recommended whenever a child's blood lead level is higher than 10 mcg/dL (CDC has now reduced this threshold to 5 mcg/dL). Those with persistent lead levels above 15-19 mcg/dL (remain elevated for 3 months or more) and those with initial tests greater than 20 mcg/dL should have their home surroundings evaluated to determine the source of the lead exposure.
For screening adults: Blood lead tests may be ordered to screen people in the workplace if lead contamination is a possibility. Family members also may be screened because lead can be carried home on clothing. This testing conforms to federal and state laws for occupational exposure.
There is not yet a national guideline for blood lead screening in adults as there is for children. The clinical cut-off values for elevated blood lead currently vary from state to state. According to the CDC's Adult Blood Lead Surveillance program (ABLES), a national health objective is to reduce all blood levels in adults to less than or equal to 25 mcg/dL.
Adults who work in industries known for lead exposure, such as smelter facilities, lead plating, auto repair, and construction, should be screened for lead exposure. Adults who have hobbies that involve lead-based paints, ceramics, or gasoline also should be tested. For a list of hobbies that may expose someone to potentially high levels of lead, go to Lead Poisoning.
The Occupational Safety and Health Administration (OSHA) has developed rules for monitoring for lead in the workplace. OSHA requires that employee blood monitoring programs be triggered by the results found in an initial air monitoring program. If a worker has an initial blood lead test result of more than 40 mcg/dL, for example, testing should be done every two months until two consecutive lead tests show a blood lead level below 40 mcg/dL. Higher levels call for closer monitoring.
For diagnosis: For both children and adults, lead testing may be ordered when a person's symptoms suggest potential lead poisoning. These symptoms are non-specific and may include fatigue, changes in mood, nausea, prolonged stomach distress, headache, tremors, weight loss, peripheral neuropathy, anemia, reproductive failure, encephalopathy, memory loss, seizures, and coma. Many children have no physical symptoms at the time of the exposure, but potentially permanent damage can still be occurring. Testing for lead exposure should be considered in children presenting with growth failure, anemia, sleep problems, hearing loss, or speech, language or attention deficits.
The higher the test result, the more lead is in the blood. However, the amount of lead in the blood does not necessarily reflect the total amount of lead in the body. This is because lead travels from the lungs and intestinal tract to the blood and organs, and then is gradually removed from the blood and organs and stored in tissues such as bones and teeth. The danger that a particular lead level represents depends on the age and health of the person, the amount of lead they are exposed to, and the amount of time that they are exposed to elevated lead levels.
Exposure to lead is not healthy for anyone, but children are more vulnerable to its effects. The national health goal has been to have every child's blood lead level below 10 mcg/dL by the year 2010. Any test results above this level trigger management and monitoring. Recent studies suggest that there may not be any safe lead level for children, that even below 10 mcg/dL, some children will have cognitive impairment. As a result, the CDC's Advisory Committee on Childhood Lead Poisoning Prevention (ACCLPP) made the recommendation in early 2012 to lower the blood lead level threshold for children from 10 mcg/dL to 5 and the CDC announced acceptance of this recommendation in May 2012.
For non-pregnant adults, a level below 25 mcg/dL is generally considered to be acceptable. If a worker has levels above 40 mcg/dL, he must be removed from lead exposure until his blood lead level drops below 40 mcg/dL. Removal may also be recommended if he is symptomatic at any level below 70 mcg/dL. Because lead will pass through the blood to an unborn child, pregnant women need to limit their exposure to lead to maintain a blood level below 10 mcg/dL and as close to zero as possible to protect the developing fetus.
Most experts agree that a child with a lead level greater than 45 mcg/dL should be treated with succimer in the hospital unless the patient is encephalopathic. Any lead level greater than 70 mcg/dL, whether in a child or an adult, should be considered a medical emergency.
Any child who has an elevated blood lead level needs to have their home or other environment evaluated. Other people at the residence should be tested as well. Without the elimination or reduction of the source of the exposure - a lead hazard in the environment - the elevated lead level will likely recur.
Poisoning with lead is more harmful for children, whose brains and other organs are still developing. Adults tend to recover from lead ingestion better than children. Children who may be at risk should be screened as soon as possible.
Lead interferes with the absorption of iron. Children with raised blood lead concentrations should be tested for iron defiency.
Each person eliminates lead differently. Thus, laboratory tests are just one part of the picture in lead poisoning cases. Careful monitoring with medical examinations is needed.
Physicians should be aware that cultural practices and folk remedies, including soil ingestion, can increase a person's risk of lead exposure. Folk remedies prepared by newly immigrated populations from Southeast Asia are particularly known as possible sources of lead. Other potential lead sources include imported foods, candy, cosmetics, costume jewelry, brass keys, and toys or household items containing or painted with lead.
This article was last reviewed on April 3, 2012. | This article was last modified on June 16, 2015.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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