Epstein-Barr-Nuclear-Antigen-IgG test is used to detect the presence of antibodies for Epstein-Barr virus. The test helps diagnose infection with the virus, which causes mononucleosis. Pregnant women may also have to undergo this test along with several other tests if they show symptoms of viral infection. The test may also be performed in individuals who have been in contact with a person suffering with mononucleosis. Your doctor may order an Epstein-Barr-Nuclear-Antigen-IgG test if you show symptoms like extreme weakness, fever, fatigue, sore throat, headache, enlarged liver/spleen/or both, and swollen lymph glands. Repeat tests may be ordered to monitor treatment outcomes.