Apr

22

How The RAST Allergy Test Works

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allergy_testingThe RAST allergy test or radioallergosorbent testing is performed by a variety of different methods but the basic fundamentals remain the same. Using blood drawn from the patient IgE and IgG antibodies responsible for producing immune reactions are measured when introduced to a series of possible allergens. To do this the original tests IgE antibodies were labeled with a radio active substance so they can be counted with a geiger counter or by some other method. Many feel that this test is less accurate although companies responsible for the testing claim new methods are more accurate than previous RAST testing. The radioallergosorbent allergy type test is marketed under various commercial names including RIST, MAST, and STALLERZYM.

History of RAST Allergy Testing

RAST  was invented in 1974 by Swedish Pharmacia Diagnostics AB. The company came out with a newer version in 1989 known as immunoCAP and designed it to be more accurate and sensitive than the original. Of course other companies have followed and offer similar testing under different brand names like RIST, MAST and STALLERZYM. Newer test are claimed to be able to also measure the severity of a allergy based on IgE numbers.

Possible RAST Testing Advantages and Uses

  • A RAST test is sometimes used if the patient is taking long acting anti histamines
  • The test maybe beneficial for those who are at risk to a severe allergic reaction. It is also useful for the elderly and those who have compromised immune systems where a severe allergic reaction from a skin test could be dangerous.
  • Can be used when skin testing does not provide a definitive result.
  • Might also be used for someone who has extreme anxiety towards skin testing.
  • The test is less time consuming than a skin or patch test.
  • RAST can be used if a skin condition is so widespread that it is difficult to find a spot for skin testing.

Possible RAST Testing Negatives

  • Much of the research done in the past shows it is less accurate than skin prick or scratch testing.
  • The cost of RAST testing is 3 to 5 times more than skin testing, those who do not support RAST testing believe price and profit are responsible for the tests popularity.
  • RAST tests can not measure sensitivities and allergens that do not produce a antibody response.


Other Blood Tests
Cytotoxic: Though not believed to be reliable by much of the mainstream medical community. Cytotoxic tests looks at leukocyte white blood cells and watches to see if their is any breakdown when allergens are introduced. Critics of the test say that it is not reliable because white blood cells react differently when outside the body. The handful of those who use the test claim to be able to use it to diagnose everything from cancer to allergies.

Histamine Release: This test is similar to the cytotoxic were basophil white cells are used.