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The Test Sample
What is being tested?
A heavy metals panel is a group of tests that measures the quantity of specific potentially toxic metals in the blood, urine or, more rarely, in the hair or other body tissue or fluid. A laboratory may offer several different groupings of heavy metals panels as well as tests for individual metals. The most common combination includes lead, mercury, and arsenic. Other panels may include one or more additional metals, such as cadmium, copper, or zinc. A healthcare practitioner will select which metals to test for based upon what a person may have been exposed to in addition to clinical symptoms.
The term "heavy metals" is loosely defined. It is related to the periodic table of elements and refers to a variety of elements with high density or metallic properties. These elements are found naturally throughout the environment and are also used by industries to manufacture a wide range of common products. Some of them, such as iron, copper, selenium, molybdenum, and zinc, are required in trace amounts by the body for normal function but can be toxic at higher levels. Significant concentrations of any of the heavy metals can be irritating or damaging to the body and can contaminate soil, air, food, and water, persisting indefinitely in the environment. Because they are a source of potential injury, the term "heavy metals" is frequently used interchangeably with the term "toxic metals."
The signs and symptoms that a person may experience depend upon the type of metal, its form, the quantity, the length of exposure, the type of exposure, the age of the person, and the person's general state of health. Some metals are much more toxic than others, and one form of a metal may be more harmful than other forms, such as an organic versus an inorganic metal compound. How a person is exposed can influence the amount of metal absorbed and the part(s) of the body that are affected. For example, a metal that does little when it is held in someone's hand, or is only moderately harmful and poorly absorbed when swallowed, may be much more toxic and cause severe lung damage when its vapors are inhaled.
Severe acute exposure can cause damage and, in some cases, can be life-threatening, but moderate exposures over time should also be monitored. The body is able to process small amounts of heavy metals, but moderate to large quantities can accumulate in the kidneys, liver, bones and brain. Some metals are considered carcinogenic – they increase the risk of developing cancer – and some can affect the body's ability to produce red and white blood cells. Fetuses and young children are at the highest risk because exposures to low or moderate concentrations can affect physical and mental development and can permanently damage the organs and brain. Many of the metals can be passed from the mother to the fetus, and some can be passed to the infant in breast milk.
How is the sample collected for testing?
Heavy metal testing is usually performed on a blood sample obtained by inserting a needle into a vein in the arm or on a 24-hour urine collection. Special metal-free blood or acid-washed urine containers are used to minimize the potential for sample contamination by any outside sources of metal.
Urine and blood can both be used for heavy metal testing, but they do not necessarily test for the same forms of a metal. For instance, methylmercury – an organic highly toxic form of mercury found in fish – can be detected in the blood but not in urine. Urine is the preferred sample for measuring inorganic forms of mercury and for measuring arsenic.
Hair and fingernail analysis can give an indication of exposure that has occurred over time or in the past but does not show recent exposures. Blood and urine will reflect exposures that are chronic or that have happened in the last few days.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
Refrain from eating seafood 48 hours before sample collection. If you have had a procedure in which either gadolinium- or iodine-containing contrast media has been administered, wait 96 hours before sample collection.