Which test detects antibodies to food antigens?

• A. Western blot
• B. Skin prick test
• C. ELISA
• D. PCR

Answer: (C)

Understanding this question comes down to how the test detects antibodies to a specific food protein. ELISA works by exposing a plate to the food antigen and then adding the patient’s serum. If antibodies against that antigen are present, they bind to the coated antigen. A secondary antibody that recognizes human antibodies and is linked to an enzyme is then added; when a substrate is added, the enzyme produces a color change. The color intensity reflects how much antibody is present, giving both a yes/no result and a measurement of antibody level to that food antigen. This direct detection of specific antibodies in the blood is why ELISA is the best choice for identifying antibodies to food antigens.

In contrast, the other tests measure different things: Western blot also detects antibodies but is more complex and typically used for detailed confirmation of specific protein-antibody interactions rather than routine screening for food antibodies; the skin prick test assesses immediate allergic reactions on the skin (IgE-mediated) rather than circulating antibodies in serum; PCR looks for genetic material and does not detect antibodies at all.