Clinical allergy diagnostics: The RAST (radioallergosorbent) test is commonly used to detect which target in patient samples?

Introduction / Context:
RAST (radioallergosorbent test) is a classic in vitro assay used to support the diagnosis of IgE-mediated (type I) hypersensitivity. It helps clinicians correlate sensitization with clinical history when skin testing is contraindicated or impractical.

Given Data / Assumptions:

• The assay uses allergen coupled to a solid phase.
• Patient serum is the sample.
• A radiolabeled anti-IgE reagent detects bound human IgE.

Concept / Approach:
RAST detects allergen-specific IgE antibodies in serum. Allergen on the solid support captures specific IgE; radiolabeled anti-IgE reveals its presence. The readout reflects sensitization, not the allergen molecule itself or active infection.

Step-by-Step Solution:
Allergen is immobilized → incubate with serum to bind specific IgE.Add radiolabeled anti-human IgE to detect captured IgE.Wash and measure radioactivity proportional to allergen-specific IgE.Therefore, RAST measures IgE antibodies associated with allergies.

Verification / Alternative check:
Modern nonradioactive analogs (e.g., ImmunoCAP) still quantify specific IgE, confirming the same principle.

Why Other Options Are Wrong:

• Allergen (antigen) is not the analyte measured; it is the capture reagent.
• Bacteriophages are unrelated to allergy testing.
• “None” is incorrect because IgE is exactly what is measured.

Common Pitfalls:
Confusing detection of allergen-specific IgE with total IgE; RAST is typically allergen-specific.

Final Answer:
antibodies associated with allergies (IgE)