Introduction Definition conceptually identical to precipitation and denotes antibody complexes with relatively large particles (e.g., RBCs) examples include an antibody binding to a bacterium or RBC which can cause it to clump (agglutinate) Clinical test examples Coombs test an agglutination test which can be divided into direct Coomb test tests for the presence of antibodies found directly on the RBC surface indirect Coomb test tests for the presence of antibodies in the serum Monospot test an agglutination test used in the work-up of Epstein-Barr virus infection which uses horse or sheep substrate