The Mononucleosis Test is a qualitative blood test that detects heterophil antibodies, which are antibodies produced in response to Epstein-Barr virus (EBV) infection. This test is used to diagnose infectious mononucleosis, commonly known as 'mono' or 'the kissing disease.' The test detects antibodies that appear during the acute phase of EBV infection and typically become positive within 1-2 weeks after symptoms begin. A positive test result, combined with clinical symptoms like fever, sore throat, swollen lymph nodes, and fatigue, confirms the diagnosis of infectious mononucleosis. However, approximately 10% of EBV mononucleosis cases may test negative for heterophil antibodies, requiring additional EBV-specific testing for confirmation. This test is particularly useful for distinguishing mononucleosis from other viral infections with similar symptoms and helps guide appropriate treatment and management decisions.