Allergy Tests

The measurement of immunoglobulin E is a good method of diagnosing an allergy and determining what the cause is. One method used is the radioallergosorbent test (RAST). If skin testing has been performed and a questionable result is obtained, it can be confirmed by RAST. Two drawbacks to this test are expense and the results are not available immediately.

This is a test used to identify particular allergens (something that causes an allergy, like a pollen). It is also sometimes used to monitor the effectiveness of immunotherapy treatment. It is a test which may be used if you have symptoms such as hives, dermatitis, rhinitis (nasal congestion or runny nose), red itchy eyes, asthma, or abdominal pain that your caregiver suspects may be caused by an allergy.

The allergen-specific IgE antibody test may also be done to monitor immunotherapy or to see if a child has outgrown an allergy, although it can only be used in a general way; the level of IgE present does not correlate to the severity of an allergic reaction, and someone who has outgrown an allergy may have a positive IgE for many years afterward.

PREPARATION FOR TEST

No preparation or fasting is necessary. A blood sample drawn from a vein in your arm. The allergen-specific IgE test can be done using a variety of methods. The method that has been used and studied for the longest time is the RAST. Some doctors refer to all IgE allergy tests as RAST even though this is a specific methodology and may not be the exact test that the lab at their institution is using. Lab values are dependent on many factors and your caregiver will help you interpret your results and what they mean to you.

NORMAL FINDINGS

  • Adult: 0-100 IU/mL

  • Child 0-23 months: 0-13 IU/mL

  • Child 2-5 years: 0-56 IU/mL

  • Child 6-10 years: 0-85 IU/mL

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.