<prompt> A patient with sore throat has a positive Paul Bunnel test. The causative organism is :EBVHerpes virusAdeno virusCytomegalovirus  <response>: Paul Bunell test is the standard diagnostic procedure of infectious mononucleosis which is caused by EBV.Paul Bunell test detects heterophile antibody.Paul Bunell testIn this test inactivated serum 56 0 C for 30 minutes in doubling dilutions is mixed with equal volumes of a 1 suspension of sheep erythrocytes.An agglutination titre of 100 or above is suggestive of infectious mononucleosis.For confirmation, differential absorption of agglutinins with guineapig kidney and ox red cells is necessaryThe Paul Bunell antibody develops early during the course of infectious mononucleosis, and disappears within two months.False positive : In patient with lymphoma hepatitis, malaria connective tissue diseaseRemember : MC cause of heterophile antibody ve infectious mononucleosis is EBV. MC cause of heterophile antibody ve infectious mononucleosis is CMV. Heterophile ve IM also caused by toxoplasmosis, Listeria, non-infectious stimuli. 