Which of the following correctly describes reverse passive agglutination?

• A. It is a negative test.
• B. It is used for identification of antigens.
• C. It can be used to detect autoantibodies.
• D. It is used to detect sensitization of red blood cells.

Answer: (B)

Reverse passive agglutination works by coating a carrier with antibody. When you mix this with a patient sample, the target antigen in the sample binds to those antibodies on the carrier, causing the coated particles to clump together (agglutinate). The visible clumping indicates the presence of the antigen, so the test is used to identify or detect antigens in the sample. It’s not about detecting autoantibodies, and it’s not primarily a test for red blood cell sensitization, which are addressed by other serologic approaches.