From the Guidelines
The main commercial RAST food panel brands currently available include ImmunoCAP (Thermo Fisher Scientific), MAST CLA (Hitachi Chemical Diagnostics), and Immulite (Siemens Healthcare), which typically test for common food allergens such as milk, egg, wheat, soy, peanut, tree nuts, fish, shellfish, fruits, and vegetables. These panels are used to diagnose food allergies and intolerances, and the specific allergens included vary by manufacturer and panel type. According to the study by 1, the most common causative allergens identified in children were milk (42%), egg (21.5%), wheat (10.9%), peanut (9.9%), and soy (8.4%).
The RAST tests measure specific IgE antibodies in the blood that react to food proteins, providing quantitative results that help clinicians assess the likelihood of true food allergies versus food intolerances. Some key points to consider when using RAST tests include:
- The tests are particularly valuable when skin prick testing is contraindicated or when patients have extensive dermatitis, dermographism, or are taking medications that interfere with skin testing.
- The negative predictive value of RAST tests is high (>95%), while the specificity and positive predictive value are low (40 to 60%) 1.
- Higher specific IgE levels and larger wheal sizes (>8–10 mm) are associated with a greater likelihood of reaction on challenge 1.
- Measuring total serum IgE levels alone, or to compare with allergen‑specific levels, is not helpful in determining food allergy 1.
Most comprehensive panels include between 20-100 different food allergens, with customization options available based on patient history and suspected sensitivities. The specific allergens included in these panels may vary, but common ones include:
- Milk
- Egg
- Wheat
- Soy
- Peanut
- Tree nuts (including almond, walnut, cashew, hazelnut, and pistachio)
- Fish (cod, salmon, tuna)
- Shellfish (shrimp, crab, lobster)
- Fruits (apple, banana, orange)
- Vegetables (tomato, potato)
It's essential to note that positive test results may reflect sensitization, associated with IgE reactivity, but have poor correlation with clinical allergic responses 1. Therefore, clinical correlation and confirmation are necessary to establish the presence of allergic disease and the exact type of allergic response.
From the Research
Current Market Brands for Food Panels in RAST Tests
There are several market brands for food panels in RadioAllergoSorbent Test (RAST) tests, including:
Allergens Included in Food Panels
The allergens included in these food panels vary, but some common ones are:
- Nuts, including Brazil nut, almond, walnut, pecan, cashew, and peanut 3
- Egg white 4
- Cow's milk 4
- Soy bean 4
- Other foods, including animals and vegetables 2
Limitations of Food Panels in RAST Tests
It's worth noting that the use of broad panels to assess sensitization to multiple foods can lead to overdiagnosis and unnecessary food avoidance, resulting in unintended consequences such as physical harm, psychological harm, and financial cost 5. Therefore, it's recommended to use these tests judiciously and in accordance with current guidelines.
Comparison of Different RAST Test Systems
Studies have compared the performance of different RAST test systems, including the Pharmacia RAST Phadebas CAP system and the AlaSTAT liquid phase EIA, and found that they have similar specificity and concordance 2. However, the AlaSTAT EIA was found to be more sensitive in detecting specific IgE antibodies in sera with low total IgE levels 2.