Premium Nahrungsergänzungsmittel | artgerecht

RAST Test – Allergy Diagnosis via Blood Test

The RAST test is a blood test used to diagnose allergies by measuring specific IgE antibodies against particular allergens in the bloodstream.

Regular tips about health Regular tips about health

Things worth knowing about "RAST Test"

The RAST test is a blood test used to diagnose allergies by measuring specific IgE antibodies against particular allergens in the bloodstream.

What is the RAST Test?

The RAST test (Radioallergosorbent Test) is a laboratory diagnostic procedure used to identify allergies. It measures whether -- and to what extent -- a patient's immune system has produced specific IgE antibodies against certain allergens. IgE antibodies are proteins of the immune system that play a central role in allergic reactions. Originally developed in the 1970s using radioactive markers, the RAST test has largely been replaced by modern, non-radioactive methods such as the ImmunoCAP test (also ELISA-based assays), which operate on the same principle and are often still referred to collectively as the RAST test.

How Does the RAST Test Work?

A small blood sample is taken from the patient. In the laboratory, the blood sample is exposed to various allergen extracts. If the patient is sensitized to a specific allergen, the specific IgE antibodies present in the blood will bind to it. The amount of bound IgE antibodies is then measured and reported in classes or concentration units (kU/L).

Result Classes

Class 0: No detectable sensitization
Class 1: Borderline sensitization
Class 2: Mild sensitization
Class 3: Moderate sensitization
Class 4-6: Strong to very strong sensitization

Important: A sensitization (positive test result) does not necessarily mean that clinical allergy symptoms are present. Results must always be interpreted in the context of the patient's medical history and complaints.

When is the RAST Test Used?

The RAST test is primarily used when a Type I allergy (IgE-mediated allergy) is suspected. Typical indications include:

Suspected pollen allergy (hay fever)
Suspected food allergy (e.g., nuts, milk, egg, wheat)
Suspected pet dander allergy
Suspected house dust mite allergy
Suspected insect venom allergy (e.g., bee or wasp venom)
Suspected mold allergy
Evaluation in cases of severe allergic asthma

The RAST test is particularly suitable when a skin test (prick test) cannot be performed -- for example, in patients with extensive skin conditions, those taking antihistamines, or those at elevated risk of anaphylactic reactions.

Advantages Over Skin Testing

No need to discontinue medications (e.g., antihistamines)
Suitable for patients with skin conditions such as eczema or psoriasis
No risk of an allergic reaction during testing
Objective, quantitative measurement of IgE concentration

Limitations and Disadvantages of the RAST Test

Less sensitive than the prick test for certain allergens
No immediate visible reaction -- results are only available after several days from the laboratory
Higher cost compared to skin testing
A positive result does not automatically confirm a clinically relevant allergy

Diagnosis and Clinical Interpretation

The RAST test is typically ordered and evaluated by an allergist or immunologist. Results are always assessed in the context of the patient's medical history, symptoms, and, if necessary, additional diagnostic procedures such as the prick test or a controlled provocation test. Interpreting RAST test results in isolation, without clinical context, is not sufficient for a reliable allergy diagnosis.

References

Matricardi PM et al. - EAACI Molecular Allergology User's Guide. Pediatric Allergy and Immunology, 2016.
Muraro A et al. - EAACI food allergy and anaphylaxis guidelines: diagnosis and management of food allergy. Allergy, 2014.
Allergy and Asthma Network - Understanding Allergy Testing: RAST and ImmunoCAP. allergyasthmanetwork.org, 2022.

Building Blocks for a Healthy Life

As an integrated manufacturer, we develop & produce evidence-based, patented, and non-patented formulations. We work exclusively with plant and natural extracts according to the strictest purity & quality standards.
The combination of science & modern technology with the laws of nature creates solutions consistently tailored to humans – for the highest good: health.