Because approximately 85% of women and men are asymptomatic,[9] a high index of suspicion is warranted based on patient history and presence of risk factors.

Typical risk factors include an age under 25 years, sexual activity with an infected partner, a new sex partner or multiple sex partners, a sex partner with other concurrent sex partners, history of a prior STI, and not using condoms.

Diagnosis and treatment is relatively straightforward once clinical suspicion is present.[9][10]

Signs and symptoms

Women may experience postcoital or intermenstrual bleeding, an odorless vaginal discharge, dysuria, or pelvic pain. The infection can ascend to the upper urogenital tract and cause fever, chills, myalgias, nausea, vomiting, and pelvic or abdominal pain. In rare cases it can cause fever and right upper quadrant abdominal pain secondary to a pericapsular hepatic infection. Examination of the cervical os may reveal a cloudy or yellow discharge. The cervix may bleed easily when rubbed with a Dacron swab.

Men may have dysuria and a clear-to-whitish urethral discharge. There may be a visible penile discharge on physical examination. If there is no visible discharge, pressure along the penile shaft may extract fluid from the base to the tip. Mild to severe scrotal pain may occur in ascending infections that cause epididymitis or prostatitis.[2] For severe infections, symptoms include fever, nausea, and vomiting. The scrotal area is tender to touch and feels warm.

Symptoms and signs of rectal infection are rare, but when present may include mucopurulent rectal discharge or tenesmus.

Diagnostic tests

Nucleic acid amplification tests (NAATs) are currently recommended.[4] The sensitivity for NAAT is >90% and the specificity is 94% to 99.5%.[11] Positive NAAT results indicate that Chlamydia trachomatis is present and should be treated. False-positive NAAT results due to residual nonviable DNA can occur for up to 3 weeks after successful treatment.[4] A negative test performed when clinical suspicion for infection is high should be repeated, as there is a possibility of false-negative results. Once an infection has been diagnosed, rigorous contact tracing is necessary to identify asymptomatic carriers.

NAATs can be done on self-collected (first-pass urine sample or vaginal swab) or clinician-collected samples (vaginal, endocervical, or urethral swab).

Rectal and oropharyngeal C trachomatis infection can be diagnosed by testing at the anatomic site of exposure. In the US, NAATs are not FDA-cleared for use with rectal or oropharyngeal swab specimens. However, some laboratories have met Clinical Laboratory Improvement Amendments (CLIA) of the Centers for Disease Control and Prevention requirements for NAATs testing validation and can perform these tests.[11] There is also good evidence that performance of NAATs on patient self-collected rectal swabs is comparable to clinician-collected rectal swabs, and patients find this self-collection method for chlamydial screening highly acceptable.[12][13]

If NAAT is not available, nucleic acid hybridization and transformation tests, enzyme immunoassays, and direct fluorescent antibodies tests should be used.

Testing can be done by cell culture (e.g., cultivation in McCoy cell culture) but it is expensive, difficult to perform, and requires special techniques.[11] Specificity is close to 100% but sensitivity is 70% to 90% depending on the laboratory and collection technique.[11] Due to variability and expense, this test should only be used in cases where legal issues are involved.

The CDC recommends empiric antibiotics for immediate treatment if there is a high index of suspicion for infection.

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