Which statement best describes passive agglutination reactions used for serodiagnosis?

Passive agglutination reactions are characterized by the use of carrier particles, such as latex particles, that are coated with antigens. This means that the antigens are not naturally present on the particles; instead, they are attached or adsorbed to them. The primary purpose of using these carrier particles is to facilitate the detection of antibodies in a sample by agglutinating (clumping together) with specific antibodies present in the serum being tested.

In passive agglutination, the interaction between the antigen-coated carrier particles and the antibodies leads to visible clumping, which can be easily identified. This approach enhances the sensitivity and specificity of the serological tests used for diagnosing various infectious diseases or autoimmune conditions.

Options suggesting a rapid single-step process, the requirement of a second antibody, or biphasic incubation do not accurately capture the essence of passive agglutination reactions. Therefore, the statement regarding the use of carrier particles is the best descriptor for this type of agglutination reaction in the context of serodiagnosis.