Paper Radioimmunosorbent Test (PRIST)

Total IgE levels.

• To monitor the effectiveness of treatment and to predict recurrence in patients with allergic bronchopulmonary aspergillosis, a fungal infestation of the airways.
• Occasionally used to measure total levels of IgE antibodies in the blood. This helps interpret results of RAST in people with diseases such as atopic dermatitis that result in high IgE levels.
• May predict allergic disorders in infants when performed on blood taken from the umbilical cord.

IgE is the most common antibody produced in allergic reactions. A high concentration in the blood usually indicates that an allergy (or allergies) is present but does not identify specific allergens.

No procedures involving radioactive substances in your blood should be done in the days prior to this test.

Blood is drawn from a vein in your arm and sent to a laboratory for analysis using a method similar to that of RAST (see above).

Follow procedures for venous blood drawing.

• Injection of radioactive substances into your blood (from other tests) prior to testing.
• IgE levels can be elevated by parasitic or viral infections, immune abnormalities and other diseases, tobacco smoking, and certain other environmental factors.

The results show the total amount of IgE antibodies in a milliliter of serum. Their interpretation depends on the reason for ordering the test. For example, if a RAST is to be performed on a person with atopic dermatitis, a PRIST might be done first to establish total IgE level. Since IgE levels tend to be extremely high in people with this skin disorder, the RAST results will only be meaningful if the total IgE levels are known.

The risk to the patient is negligible.

• Results correspond poorly with the individual's predisposition to allergy.
• It's at least twice as expensive as skin testing.
• Results are not immediately available.

Usually, no further testing is necessary; however, determining the levels of other antibodies, such as IgA, IgG, and IgM (see below), may be helpful in interpreting results.