RAST and PRIST
RAST and PRIST are blood tests used to show whether a person has an allergy and to try to identify which specific substance they are allergic to.
Why they are done
These tests are recommended by the doctor when there are symptoms suggesting an allergic reaction.
How they are done
RAST and PRIST are simple blood tests. No special preparation or fasting is needed for these tests. Medicines, except antihistamines and cortisone (used to suppress allergy symptoms), do not affect the result, although your doctor should always know which medicines you are taking.
Results
NORMAL VALUES
PRIST (total IgE) under 1 year up to 3 IU/ml
1-2 years up to 17 IU/ml
2-3 years up to 26 IU/ml
3-9 years up to 70 IU/ml
9-15 years up to 155 IU/ml
over 15 years up to 91 IU/ml
RAST kU/l Class
0-0.34 0 Negative
0.35-0.69 1 Very low level
0.70-3.50 2 Low level
3.51-17.49 3 High level
17.50-100 4 Very high level
over 100 5 Extremely high level
What they mean
PRIST test or total IgE (immunoglobulin E):
If the value is higher than normal, this is an abnormality indicating that the person has an allergy. At this point it is advisable to investigate further with a RAST to try to identify the substance the person is allergic to.
If the value is normal but the person clearly has all the symptoms of an allergy, it is still advisable to perform a RAST, because in some allergic people the PRIST is normal.
RAST test or specific IgE (immunoglobulin E): this test looks specifically for antibodies against particular substances, for example whether antibodies against pollen, dust mites, strawberries, milk, wood and so on are present.
If the value for a given allergen is normal, you are not allergic to that substance.
If, however, the value is higher than normal, you are allergic to that substance. Moreover, the higher the value, the stronger the allergy. Several substances to which you are allergic can also be identified at the same time.