In which zone might an antibody-screening test be false negative?

In which zone might an antibody-screening test be false negative?

• A. Prozone
• B. Zone of equivalence
• C. Postzone
• D. None of the above

Answer: (A)

The key idea here is the prozone phenomenon: when antibody is in excess relative to antigen, there aren’t enough cross-linking points to form the lattice networks needed for a visible positive reaction. In antibody-screening tests that rely on lattice formation, this antibody excess can make the test appear negative even though antibodies are present. To reveal the true result, the serum is diluted; as the antibody concentration decreases into the zone of equivalence, cross-linking improves and a positive result may appear. So, the false negative occurs in the prozone where antibody is in excess, and dilution helps move into the zone where the reaction develops properly.

The key idea here is the prozone phenomenon: when antibody is in excess relative to antigen, there aren’t enough cross-linking points to form the lattice networks needed for a visible positive reaction. In antibody-screening tests that rely on lattice formation, this antibody excess can make the test appear negative even though antibodies are present. To reveal the true result, the serum is diluted; as the antibody concentration decreases into the zone of equivalence, cross-linking improves and a positive result may appear. So, the false negative occurs in the prozone where antibody is in excess, and dilution helps move into the zone where the reaction develops properly.