Which homogeneous immunoassay relies on inhibiting the activity of the enzyme label when bound to antibody reagent to eliminate separating freelabeled from bound-labeled reagent?

Which homogeneous immunoassay relies on inhibiting the activity of the enzyme label when bound to antibody reagent to eliminate separating freelabeled from bound-labeled reagent?

• A. EMIT
• B. CEDIA
• C. MEIA
• D. ELISA

Answer: (A)

In a homogeneous immunoassay, the readout comes from a label whose activity is modulated by binding, so you don’t have to separate bound from free reagents. In EMIT, the reagent is an enzyme-labeled drug analog that binds to the antibody; this binding inhibits the enzyme’s activity. When the target analyte is present, it competes with the labeled analog for the antibody, freeing more active enzyme-labeled tracer in solution. The active enzyme then converts substrate to produce a measurable signal, and the signal changes with the analyte concentration. Because the bound labeled reagent is inactive, separation of bound and free forms isn’t needed—the signal comes from the unbound, active label. The other options involve different mechanisms or require separation steps, so they don’t fit this inhibition-based, truly homogeneous approach.

In a homogeneous immunoassay, the readout comes from a label whose activity is modulated by binding, so you don’t have to separate bound from free reagents. In EMIT, the reagent is an enzyme-labeled drug analog that binds to the antibody; this binding inhibits the enzyme’s activity. When the target analyte is present, it competes with the labeled analog for the antibody, freeing more active enzyme-labeled tracer in solution. The active enzyme then converts substrate to produce a measurable signal, and the signal changes with the analyte concentration. Because the bound labeled reagent is inactive, separation of bound and free forms isn’t needed—the signal comes from the unbound, active label. The other options involve different mechanisms or require separation steps, so they don’t fit this inhibition-based, truly homogeneous approach.