Chlamydia trachomatis Antibody, IgG

The Chlamydia trachomatis Antibody, IgG test (anti-Chlamydia trachomatis IgG) is used to document prior exposure to C. trachomatis. In combination with other serologic classes (IgM and IgA) and clinical findings, it helps contextualize the stage of infection. It may aid assessment of conditions associated with antecedent chlamydial disease, including tubal factor infertility or a history of ectopic pregnancy.

Chlamydia trachomatis is an obligate intracellular bacterium with a biphasic cycle that alternates between extracellular, antibiotic-insensitive elementary bodies and intracellular, replicating reticulate bodies. Transmission occurs through mucosal contact, most commonly via sexual exposure; perinatal spread can occur during passage through the birth canal. The organism targets columnar epithelial cells of the urethra, endocervix, rectum, conjunctiva, and oropharynx. The usual incubation period is 7 to 20 days, and infection may be asymptomatic or minimally symptomatic while tissue damage accrues. In women, infection often manifests as cervicitis and may ascend to endometritis and salpingitis, producing tubal injury with risk for infertility or ectopic pregnancy; extension to the peritoneum can occur. In men, the typical presentation is nongonococcal urethritis, with possible involvement of the epididymis; prostatitis may develop. Perinatal infection can lead to neonatal conjunctivitis or pneumonia. Lymphogranuloma venereum represents a distinct invasive syndrome caused by specific serovars. Humoral immune responses include IgM, IgA, and IgG, which arise at different times in the course of infection. IgG generally becomes detectable 3 to 4 weeks after a primary infection and may be present during active disease as well as for a prolonged period after resolution, serving as an indicator of past infection.