Also known as:Chlamydia NAAT or NAT; Chlamydia/GC STD Panel
Formal name:Chlamydia trachomatis by Nucleic Acid Amplification Test (NAAT); Chlamydia trachomatis Culture; Chlamydia trachomatis DNA Probe
Related tests:Gonorrhea Testing, HIV Antibody and HIV Antigen, Syphilis Tests, Herpes Testing, HPV Test, Trichomonas Testing
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Why Get Tested?
To screen for and diagnose a chlamydia infection
When to Get Tested?
- For women, yearly testing recommended if you are sexually active and younger than age 25 or 25 or older and at increased risk for this sexually transmitted disease (STD); if you fall into one of these groups and are pregnant or considering pregnancy
- For men, yearly testing recommended if you are a man who has sex with men
- When you have symptoms of this STD, such as pain during urination, vaginal discharge and abdominal pain (for women) or unusual discharge from the penis, pain on urination or painful, swollen testicles (for men)
- When a newborn has conjunctivitis
For women, a swab or brush of cells or secretion from your vagina; for men or women, the initial portion of your urine stream (first-catch urine sample); sometimes a swab of cells or secretion from a non-genital area that may be infected
Test Preparation Needed?
Tell your healthcare provider about any use of antibiotics or, for women, douches or vaginal creams; you may be asked to avoid using these within 24 hours before testing vaginal samples since they may affect test results. Menstruation will not affect results. For a urine sample, you may be instructed to wait one to two hours after you last urinated before collecting the sample. Follow any instructions you are given.
How is it used?
Chlamydia testing is used to screen for, diagnose, and verify successful treatment of infections caused by the bacteria Chlamydia trachomatis. Chlamydia is one of the most common bacterial sexually transmitted diseases (STD) in the U.S. and can cause serious complications if not treated. Screening for, diagnosing, and treating chlamydia is very important to prevent long-term complications and spread of the infection to others. (For more, see the "What is being tested?" section.) Photo source: CDC/James Gathany
Testing for Chlamydia trachomatis and Neisseria gonorrhoeae (gonorrhea) is often done at the same time since the infections caused by these two bacteria can have similar signs and symptoms. These bacteria may be acquired at the same time, and an an individual may have infections with both. A definitive diagnosis is important since the two infections require different antibiotic treatment. Repeat testing is recommended to ensure that treatment has been effective. This is done about three months after a person has completed treatment.
The nucleic acid amplification test (NAAT) is the recommended method of testing for chlamydia. NAAT is a molecular test that detects the genetic material (DNA) of Chlamydia trachomatis. It is generally more sensitive and specific than other chlamydia tests and can be performed on a vaginal swab on women, or urine from both men and women, which eliminates the need for a pelvic exam in women.
Besides NAAT, other chlamydia tests include culture, which grows the bacteria, direct fluorescent antibody stain (DFA), and DNA probe, but these are used less commonly since they are less sensitive to detect a chlamydia infection.
When is it ordered?
Because many infected people do not have any noticeable symptoms, a number of health organizations recommend regular screening for certain people:
All sexually active women younger than age 25 and sexually active women age 25 and older who are at increased risk should get yearly screening for chlamydia, according to the Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists. The U.S. Preventive Services Task Force (USPSTF) and the American Academy of Pediatrics also recommend routine screening for these women (the USPSTF says age 24 and younger).
Examples of risk factors for chlamydia infection include:
- Previous chlamydia infections, even if they were treated
- Having STDs, especially HIV
- Having new or multiple sex partners
- Having a sex partner diagnosed with an STD
- Using condoms inconsistently
- Exchanging sex for money or drugs
- Using illegal drugs
- Living in a detention facility
For pregnant women, the CDC recommends screening for chlamydia during the first trimester or first prenatal visit and, for those younger than 25 or who are at increased risk of infection, repeat testing in the third trimester. Pregnant women diagnosed with chlamydia should be retested about 3 months after completing treatment. (See Pregnancy & Prenatal Testing.)
The CDC recommends that men who have sex with men get chlamydia screening at least annually. Health organizations do not recommend routine screening for sexually active, heterosexual men with no symptoms. However, healthcare practitioners may recommend screening to their patients when, for example, there is a high number of cases (prevalence) of STDs in the community.
Chlamydia testing may also be done when a person's sex partner has been diagnosed with chlamydia or when a person has signs and symptoms of the infection.
For women, if symptoms occur, they may include:
- Bleeding between menstrual periods and after sexual intercourse
- Abdominal pain
- Painful intercourse
- Painful and/or frequent urination
- Abnormal vaginal discharge
For men, symptoms may include:
- Pus or milky discharge from the penis
- Painful and/or frequent urination
- Pain, tenderness and swelling of the testicles
Both men and women can get an infection in their rectum and may be tested when they have symptoms such as itching, inflammation, pain, discharge and/or bleeding from the rectum. 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.
Women or men treated for chlamydia should be retested three months after their treatment.
What does the test result mean?
A positive test indicates an active chlamydia infection that requires treatment with a course of antibiotics.
A negative test means only that there is no evidence of infection at the time of the test. It is important for those who are at increased risk to have screening tests performed on an annual basis to check for possible infection, especially since re-infection is common, particularly among teenagers.
If you are infected, your sexual partner(s) should be tested and treated as well.
Is there anything else I should know?
People who are infected have a higher risk of contracting 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.
The Centers for Disease Control and Prevention (CDC) recommends the NAAT testing method for chlamydia, except in cases of child sexual abuse in boys or rectal and oral infections in preteen girls. In these cases, culture is recommended.
What is being tested?
Chlamydia is one of the most common bacterial sexually transmitted diseases (STD) in the United States and can cause serious complications if not treated. Chlamydia testing identifies the bacteria Chlamydia trachomatis as the cause of a person's infection. Screening for, diagnosing, and treating chlamydia is very important in preventing long-term complications and spread of the infection to others.
Chlamydia infections are especially common among people 15 to 24 years of age. The Centers for Disease Control and Prevention (CDC) estimates that 2.86 million Americans are infected with chlamydia each year and notes that women are frequently re-infected if their partners don't get treatment. The actual number of cases may be higher since many people do not experience any symptoms and do not get tested and diagnosed. Still, over one million new cases are reported each year.
Chlamydia is generally spread through sexual contact (oral, vaginal, or anal) with an infected partner. Risk factors include having multiple sex partners, coinfection or previous infection with another STD, and not using a condom correctly and consistently.
Many people with chlamydia infections have no symptoms and some may experience only mild symptoms. Signs and symptoms of chlamydia are similar to and can be confused with those cause by another STD, gonorrhea, so tests for these infections are often done at the same time. (For more, see "The Test" tab.)
Chlamydia is easily treated with a course of antibiotics. If not diagnosed and treated, it can cause severe reproductive and other health problems.
In women, untreated chlamydia infections can lead to pelvic inflammatory disease (PID) from infections that start on the cervix but spread to the fallopian tubes and ovaries. This can cause:
- Long-term (chronic) pelvic pain
- An increased risk of tubal (ectopic) pregnancy, which can be fatal
Pregnant women who are infected may experience heavy bleeding before delivery and premature rupture of the membranes and/or have babies with low birth weights. Infected mothers can pass the infection to their baby during childbirth. These babies are at risk of developing complications such as pneumonia or conjunctivitis, an inflammation that, left untreated, can threaten eyesight.
Rarely, men who are not treated may become infertile.
How is the sample collected for testing?
For women, vaginal swabs are the optimal sample for genital chlamydia testing. A healthcare practitioner may use a swab or small brush to collect a sample of cells or secretion from the vagina during a pelvic examination. Sometimes, a vaginal sample is collected by the woman who is undergoing testing (self-collection).
Urine is recommended for men, but can also be used for women. As you begin to urinate, collect the initial portion of your urine stream (first-catch) in a container provided by the healthcare practitioner or laboratory.
Sometimes, a healthcare practitioner may use a swab or brush to collect a sample of cells or secretion from other areas that may be infected, such as the urethra, penis, anus, or throat.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
Tell the healthcare practitioner about any use of antibiotics or, if you are a woman, douches or vaginal creams. You may be asked to avoid using these within 24 hours before testing vaginal samples since they may affect test results. Menstruation will not affect results. You may be instructed to wait one to two hours after you last urinated before collecting a urine sample. Follow any instructions you are given.
- How long does it take to get results?
This will depend on where the lab testing is done and the method used to diagnose the infection. Nucleic acid amplification (NAAT) methods can give results in one to a few days. Cultures take longer and results are typically reported in 5 to 7 days.
- Where can I get tested?
Visit the healthfinder.gov webpage Get Tested for Chlamydia and Gonorrhea to find out where you can get tested. You can input your zip code and find a local testing site.
- How can chlamydia be prevented?
The most reliable ways to avoid infection with chlamydia or any sexually transmitted disease are to abstain from oral, vaginal, and anal sex or to be in a long-term, mutually monogamous relationship with an uninfected partner. People who are sexually active should correctly and consistently use condoms to reduce the risk of infection with chlamydia and other STDs.
- How is chlamydia treated?
Antibiotics are prescribed to treat chlamydia. They can cure the infection, but damage from the infection may sometimes be permanent. If symptoms do not resolve after a few days, then you should consult with your healthcare provider. You should refrain from having sex until you have completed your treatment and should be re-tested three months after treatment.
- If I get treated, can I get chlamydia again?
Yes. Even though treatment will cure your infection, you can get it again if you are exposed again. In fact, reinfection is common, according to the CDC.
- Should I tell my partner that I have chlamydia?
Yes, you should tell your sexual partner(s) that you have chlamydia so that they can get tested and treated.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
Descriptions of clinical laboratory tests were originally prepared for use on Lab Tests Online, an award-winning patient education website on clinical laboratory testing. Lab Tests Online is produced by the American Association for Clinical Chemistry (AACC), a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. The Lab Tests Online website is developed in collaboration with other laboratory professional societies and is funded in part through corporate sponsorships.