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Zinc - Deficiency Test

The zinc test, an analysis by atomic absorption spectroscopy, measures serum levels of zinc. An important trace element, zinc is an integral component of more than 80 enzymes and proteins, and plays a critical role in enzyme catalytic reactions.

Zinc occurs naturally in water and in most foods; high concentrations are found in meat, seafood, dairy products, whole grains, nuts, and legumes. Zinc deficiency can seriously impair body metabolism, growth, and development.

Purpose

• To detect zinc deficiency or toxicity

Patient preparation

• Explain to the patient that this test determines the concentration of zinc in the blood.
• Inform him that he needn't restrict food or fluids.
• Tell him that the test requires a blood sample. Explain who will perform the venipuncture and when.
• Reassure him that although he may feel some discomfort from the needle and the pressure of the tourniquet, collecting the sample takes only a few minutes.

Procedure and posttest care

• Perform a venipuncture, and collect a 3-ml sample in a zinc-free collection tube.
• If a hematoma develops at the venipuncture site, apply warm soaks.

Precautions

• Handle the sample gently to prevent hemolysis, and send it to the laboratory immediately. Reliable analysis must begin before platelet disintegration can alter test results.

Reference values

Normally, plasma zinc values range from 0.66 to 1.10 ug/ml.

Abnormal findings

Decreased serum zinc levels may indicate an acquired deficiency (from insufficient dietary intake or due to an underlying disease) or a hereditary deficiency. Markedly depressed levels are common in leukemia and may be related to impaired zinc-dependent enzyme systems. Low serum zinc levels are commonly associated with alcoholic cirrhosis of the liver, myocardial infarction, ileitis, chronic renal failure, rheumatoid arthritis, and anemia (such as hemolytic or sickle cell anemia).

Elevated and potentially toxic serum zinc levels may result from accidental ingestion or industrial exposure.

Interfering factors

• Failure to use metal-free collection tube
• Hemolysis due to rough handling of the sample
• Delayed transport to laboratory
• Time of day and time of last meal (possible increase or decrease)
• Zinc-chelating agents, such as penicillinase, and corticosteroids (decrease)
• Estrogens, penicillamine, antineoplastics such as cisplatin, antimetabolites, and diuretics (possible decrease)