Chlamydia trachomatis IgG antibodies in serum (Chlamydia trachomatis Abs IgG, Serum) is a test used to detect IgG antibodies in the blood that are produced by the immune system after exposure to the bacterium Chlamydia trachomatis. This analysis helps diagnose past or previous infection with Chlamydia trachomatis, a bacterium that causes genital infections which can lead to complications such as infertility or pelvic inflammatory disease. The presence of IgG antibodies indicates that the body has been exposed to the infection at some point, even if there are no current symptoms.