The test is used:

1. to diagnose the cause of symptoms,
2. to screen sexually active people for the microorganism, or
3. to document that a person has been sexually abused.

A definitive diagnosis is important because chlamydia can resemble gonorrhea, and the two infections require different antibiotic treatment.

The preferred method of testing currently is the molecular test also known as nucleic acid amplification tests (NAAT). This test is based on amplification of the DNA that is present in Chlamydia trachomatis. Molecular testing for Chlamydia trachomatis is currently the standard and is widely utilized. The advantage of molecular tests is that they are generally more sensitive and specific than conventional culture and can therefore identify more positive specimens. Molecular tests should not be used to diagnose or verify cases with legal implications. Until the legal system changes, only a positive culture result proving infection with chlamydia is admissible in court. All positive molecular tests for Chlamydia trachomatis should be verified by the same or another methodology for confirmation. Molecular tests need to be validated for different sources of specimens. They have not been FDA approved for performance with ocular, pharyngeal, or rectal sites.

Testing for Neisseria gonorrhoeae (gonorrhea) and Chlamydia trachomatis is generally done simultaneously as the two organisms have similar clinical presentations.

A doctor may order the test if you have symptoms such as vaginal discharge and abdominal pain (for women) or unusual discharge from the penis or pain on urination (for men). However, about 75% of infected women and 50% of infected men show no active symptoms, so the Centers for Disease Control recommend testing in the following cases:

• All sexually active females under 20 years of age (test at least once a year).
• Women ages 20 and older who have one or more risk factors (test annually). Risk factors include having new or multiple sex partners, having sex with someone who has other partners, and not using barrier contraceptives, such as condoms.
• All women with an infection of the cervix.
• All pregnant women.
• Men with painful and frequent urination (dysuria), penile discharge, infection of the prostate (prostatitis), or inflammation involving the anus and rectum (proctitis).

A positive test indicates an active infection that requires treatment with a course of antibiotics.

Chlamydia is often called “the silent epidemic” because infections are so prevalent yet many people do not know that they are infected. An estimated 3 million cases occur annually in the U.S. Chlamydia is especially widespread among young people and most common in women between the ages of 19 and 25. It is four times as common as gonorrhea and six times as common as herpes.

Chlamydia is easily treated, but if left untreated, it can cause severe reproductive and other health problems. 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.