RADIO-ALLERGO-SORBENT TEST (RAST)

Avoiding allergens is an essential part of the management of allergic diseases when you are allergic to food allergy, asthma and allergic rhinitis (hay fever). Skin testing is the traditional method for diagnosis of IgE-mediated allergic disorders.

This bioassay (an analytical method to determine concentration or potency of a substance by its effect on living cells or tissues.) is highly sensitive, cost-effective, and safe when used by experienced personnel.

A laboratory technique capable of detecting small quantities of allergen-specific IgE antibodies that circulate in the serum of allergic patients is called radioallergosorbent test (RAST), that utilizes a radioimmunoassay method.

A radioallergosorbent test (RAST) is an assay used to detect the allergen specific IgE antibodies in the bloodstream. This is the most common diagnostic method performed for evaluation of allergies. RAST aids in differential diagnosis of allergies (especially food allergies), atopic asthma, natural rubber latex allergies, and psoriasis. It is also helpful in monitoring the treatment of specific allergies.

RAST Versus Skin Prick Tests

This is a blood test used, to check for allergic sensitivity to specific substances. In the test, the sample of blood is mixed with substances known to trigger allergies. It then measures the amount of IgE directed against specific allergens by binding a specific antigen to a carrier substance and allowing it to react with a specific IgE antibody (allergy antibodies), from the patient’s blood sample, to check for any allergic reaction.

RAST Procedure

Even though RAST is not as sensitive as intradermal skin testing, it has many advantages when used in conjunction with, or as an alternative to conventional test procedures.

• Safe: The results of RAST are not affected by allergic symptoms or suppressed by medication used for symptomatic treatment of allergic disease. Skin testing may worsen the condition of patients who have serious symptoms of asthma, urticaria, or atopic dermatitis.

  These skin tests cannot be performed in patients using antihistamines as these medications will suppress the results. The pricking or scratching in skin tests may create uncomfortable feeling and may result in itching and swelling. As RAST is done outside the patient, it is not affected by illness or medication.

  Especially in younger children, allergy skin testing is traumatic and rarely these patients become so anxious that allergy skin testing cannot be done. In such cases, the RAST may be a good alternative method.

• Does Not Need A Professional: While skin prick testing requires a health professional to perform the procedure and interpret the results, RAST is direct and does not require any special experience, expertise or reagents for the medical practitioner performing the test.
• No Early Preparation:RAST can be done without having to avoid antihistamine medications and drugs, few days before the test. In contrast, skin prick test using such medications 7 days before the test, would interfere with the test results. There is also no restriction on using creams and moisturizers which may cause further allergic reactions, in skin prick test due to allergen extracts that they contain.

Limitations Of RAST:

• It is less sensitive than allergy skin tests in detecting small amounts of clinically relevant IgE antibodies. Many studies have shown that false-negative results may be as high as 50% because the end-point sensitivity is set too high.
• Limited availability of allergens for RAST
• Poor quality control of RAST and its use in many commercial laboratories
• RAST is expensive.

Why BSR Hospital?

BSR ENT Hospital is one of the renowned ENT Specialist Hospital in Hyderabad and Secunderabad with a high success rate of surgeries and clinical outcomes since the past 40 years. Highly qualified, experienced and trained ENT specialists like Dr. B. Shanker Rao, MS, DLO, FICS and Dr. B. Kalyan Chakravarthy, MS ENT / Head and Neck Surgeon, are adept at delivering the best in treatment solutions for all ENT disorders.

Dr. Kalyan Chakravarthy is also a consultant with KIMS Hospitals, one of the largest corporate Hospitals group in South India with tertiary and quaternary healthcare. BSR Hospital’s ENT team are experts in their area of specialization in ENT care.

The hospital is equipped with advanced technologies, expert and patient-friendly staff. The high quality treatment is personalized and affordable. The doctor discusses the treatment plan with the patient and educates them on the condition and the required treatment to help the patient take informed decision about his/her treatment.