Testing for Chlamydia trachomatis and Neisseria gonorrhoeae (gonorrhea) is generally done simultaneously as the two organisms have similar clinical presentations. A definitive diagnosis is important since the symptoms of chlamydia can resemble those of gonorrhea and the two infections require different antibiotic treatment.
The nucleic acid amplification test (NAAT) is the preferred test. This test is based on amplification of the DNA that is present in Chlamydia trachomatis. It is generally more sensitive and specific than other chlamydia tests and can be performed on urine from both men and women, and eliminates the need for a pelvic exam in women.
The Centers for Disease Control and Prevention (CDC) recommends that victims of sexual assaults get NAAT testing for both C. trachomatis and N. gonorrhoeae, which are among the diseases most commonly transmitted in such cases, so that they can receive treatment if infected. However, molecular tests should not be used to verify cases with legal implications, such as sexual assault. Until the legal system changes, only a positive culture result proving infection with chlamydia is admissible in court.
Other chlamydia tests include direct fluorescent antibody stain (DFA), which detects chlamydia antigens, and DNA probe, another test that looks for chlamydia DNA but that is less sensitive than NAAT.
A health care provider may order a chlamydia test if someone has symptoms such as vaginal discharge and abdominal pain (for women) or unusual discharge from the penis or pain on urination (for men). However, because many infected people do not have any symptoms, a number of organizations have published screening recommendations.
The CDC, the U.S. Preventive Services Task Force (USPSTF), the American Academy of Family Physicians (AAFP), and the American College of Obstetricians and Gynecologists (ACOG) all recommend chlamydia screening for sexually active women under age 25 (CDC says age 25 and younger) and for all other sexually active women who are at increased risk. CDC and ACOG specifically recommend annual screening.
These organizations do not recommend routine screening for sexually active, heterosexual males. Health care providers may, however, use their judgment and consider risks, such as prevalence of these STDs in the community. The CDC does recommend that sexually active men who have sex with other men have chlamydia screening at least annually.
A person may be at increased risk for chlamydia if they:
For pregnant women, the CDC recommends screening for chlamydia during the first prenatal visit and again in the third trimester for those 25 and younger or who are at increased risk of infection. Pregnant women diagnosed with chlamydia during the first trimester should be retested within 3 to 6 months, preferably in the third trimester. (See Pregnancy & Prenatal Testing.)
Testing for both chlamydia and gonorrhea may be done when a newborn has symptoms of conjunctivitis, such as redness and swelling of the eye, and discharge.
A positive test indicates an active infection that requires treatment with a course of antibiotics.
A negative test means only that there is no evidence of disease at the time of the test. It is important for those who are at increased risk of infection to have screening tests performed on a regular basis to check for possible exposure, especially since re-infection is common, particularly among teenagers.
If you are infected, your sexual partner(s) should also be tested and treated as well.
People who are infected have a higher risk of developing other sexually transmitted diseases, including a 3 to 5 times greater risk of acquiring HIV if exposed to it.
Molecular tests are only FDA-approved for use with urine samples or samples from genital sites such as the vagina and penis; they have not been FDA-approved for performance with ocular (eye), pharyngeal (throat), or rectal samples. Individual laboratories may perform molecular testing on these samples, but they are required to validate the methods themselves.
This article was last reviewed on September 26, 2012. | This article was last modified on June 25, 2014.
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