Allergy Immunology Service

RAST SYSTEM FOR THE DIAGNOSIS AND TREATMENT OF ALLERGIES

Micro-Screen

Serolab offers a RAST screen for a total of eight allergens at a nominal price. Six of the allergens are pollens and are coupled to the same disc. The remaining two allergens are House Dust Mite and Alternaria attached to a second disc.

SEASONAL SCREEN
Short Ragweed
English Plantain
Oak
Elm
June Grass (Kentucky Blue)
Bermuda Grass

PERENNIAL SCREEN
House Dust Mite
Alternaria

The use of these eight allergens incorporates representatives from the five major antigen classes: weed pollens, grass pollens, tree pollens, mites (one of the major antigens in house dust) and mold.

A positive to the seasonal screen would indicate an Allergy to pollens (classic hay fever) and should be followed with further testing of relevant pollen allergens. A negative on the seasonal screen, but a positive on the perennial screen would indicate further testing on mite, molds and other household allergens such as cat hair and dog hair. Obviously, a positive to both the seasonal and perennial screens would indicate further testing for both pollens and other perennial allergens.

This screening technique provides a very cost effective method for assessing the patient’s response prior to extensive testing. The test results are strictly screening results and should be used for this purpose only; immunotherapy can not be initiated on the basis of micro-screen results.

A Total IgE should be performed on every patient tested to establish a “baseline” for possible use later, and can also be a very valuable indicator in the event no positives are found: a low Total IgE would confirm the patient is probably negative while an elevated Total IgE, with no individual positives, might indicate further testing is warranted. A patient with highly elevated Total IgE can be suffering from health issues not related to Allergy.

Mini-Screen

The mini-screen technique involves testing a patient for 7 to 10 selected allergens. Individual RAST tests for representatives of tree pollens, weed pollens, grass pollens, mite and a major mold are easily selected for different regions to comprise a mini-screen. When at least 8 allergens are used for the mini-screen, efficiency and sensitivity of the test are both in excess of 95%.

If all responses on the mini-screen are negative, further RAST testing is not indicated. Positive response to pollens but not to mite or molds would indicate further testing of pollens only; the reverse is true if positive responses are observed in only mite and molds.

One of the major advantages of the mini-screen is the efficiency when positive test results are received. Only additional allergens need be tested. The results of the mini-screen tests can later be used for calculation of initial doses for immunotherapy after further testing is performed on the additional allergens.

Patient Work Up (Battery)

Most Physicians complete the allergic patient’s work-up with a battery of RAST tests in the range of 20-25 total allergens, (depending on screen indications) plus a Total IgE. The initial use of a screen provides the Physician with confidence that results from the final battery will be positive. The specific antigens, and each antigen concentration appropriate for treatment are easily determined from the RAST test results.

Patient Treatment Sets

It has been repeatedly demonstrated that specific immunotherapy for Allergy is far superior to any other type of immunotherapy. This means the best chance for successful immunotherapy, (thus patient satisfaction) is by tailoring the treatment mixture according to the patient’s level of sensitivity to each specific allergen. Some commercial laboratories do not offer treatment sets formulated according to the patient’s allergen sensitivity levels, but instead, include all antigens shown to be positive by RAST in the mixture at the same volumes and/or the same concentrations. Use of a general immunotherapy program as described negates the need for determining the level of sensitivity of the patient to each allergen but can result in a high rate of immunotherapy failures.

Once the final battery of tests is complete, then the Physician can mix the treatment set in his office or order the antigen mixture in the appropriate concentrations using the RAST results as a guide. When the treatment set has been prepared it is recommended that a “vial test” (intradermal skin test) be applied prior to subcutaneous injection of the first dose as a safety test. Technical assistance and literature for formulation of treatment sets, “vial testing,” and dosing regimen are available from Serolab.