Skin test anergy

Alternative names:

anergy screen

What the risks are:

A very small amount of the antigen is injected, so the risks are minimal. Typical reactions include itching and hives.

A patient who is hypersensitive to the antigen may experience respiratory distress or other signs of anaphylactic shock.

Special considerations:

Some skin tests are less accurate than others. 20 to 30% of patients with tuberculosis have negative tuberculin skin tests. Tetanus immunization (vaccine) can cause false positive results for diphtheria (Schick test). Tests for food allergies may be less accurate than disease antigen testing.

Other factors that can affect the test results include:

• where on the body the test is performed (the arm reacts differently than the back)
• the time of day (morning tests react differently than afternoon tests)
• proximity (closeness) to other tests
• antihistamines can cause a false negative test (negative results when the antigen should show reaction)
• old antigens