How Chlamydia Is Diagnosed

Chlamydia is a sexually transmitted infection (STI, formerly called sexually transmitted disease, or STD, that often has no symptoms. Despite this, chlamydia can cause complications that can ultimately lead to infertility and other concerns.

Unfortunately, there isn't a home test you can use to detect it, and the symptoms of chlamydia aren't considered proof of infection. Testing with a urethral swab, a swab of the cervix or vagina, or a urine test can determine whether you have an infection and require treatment.

Self-Checks

There is no way to self-test for chlamydia. Chlamydia can only be properly diagnosed in the clinic using specific lab tests. You may look up the symptoms of chlamydia, and they are good to be aware of. But there is considerable overlap between them and those of other medical conditions. Also, many people do not have symptoms with a chlamydia infection.

Labs and Tests

There are a few different tests to look for the presence of Chlamydia trachomatis, the bacterium that causes this STI. These tests can be performed if you have symptoms or as a routine screening if you are sexually active.

The most common tests are nucleic acid amplification tests (NAATs). These can be run on a:

• Urine specimen
• Urethral swab (in people with penises, a swab of the tube through which urine passes out of the body)
• Endocervical swab (a swab of the area around the opening of the uterus)
• Vaginal swab (a swab of the walls of the vagina)

Healthcare providers and clinics differ in which tests they prefer.

It is possible to test for chlamydia with a urine sample. However, not all practitioners are willing to perform urine tests on women. Many healthcare professionals prefer to use cervical samples, as they have historically been thought to provide more accurate results.

That said, if you are less likely to get a chlamydia test if it requires a swab, ask for a urine test. It may not be quite as reliable as a swab, but it's still a very good test.

Note that a Pap smear, a routine gynecological procedure that screens for cervical cancer, does not look for chlamydia. A Pap test also cannot detect Chlamydia trachomatis. 

Likewise, if you've been tested—or treated—for other sexually transmitted infections, don't assume that chlamydia was included. Not only does chlamydia require its own test, but the treatments for some of the other STIs are ineffective against chlamydia.

What to Expect

The way that healthcare providers test for chlamydia is somewhat different for people with a vagina and a uterus and people with a penis. This is due to the locations the bacteria infect in each group.

People With a Vagina and Uterus

For an endocervical swab, your gynecologist will insert a speculum, a device that helps keep your vaginal walls open, to view your cervix. They will use a thin swab to retrieve a sample from your cervix, which will then be sent to a lab.

Less commonly, a vaginal swab may be done, which requires inserting a swab into the vagina and gently rotating it to collect a sample. Studies suggest that vaginal swabs that people do themselves are just as accurate (if not more so) than those performed by healthcare professionals. However, in most circumstances, a healthcare provider will recommend that they do the swab.

If you are opting for a urine test, be sure to come to your healthcare professional's office with a full bladder. 

People With a Penis

Your healthcare provider will either ask you for a urine sample or collect a sample from inside the head of your penis using a small swab. This sample is then sent to a lab for analysis.

Not all practitioners perform urine tests for chlamydia. However, you should feel comfortable asking whether getting a urine test for chlamydia is an option. You can also call your healthcare provider in advance to see if urine testing is available.

What About Rectal and Oral Swabs?

Rectal swabs and oral swabs may also be considered for those who have receptive anal sex or unprotected oral sex.

While neither rectal nor oral swabs are currently approved for the detection of chlamydia, research suggests that doing these extragenital tests (outside the genital region) is important.

For example, a 2017 study found that among men who have sex with men (MSM), 13% had a rectal chlamydia infection but only 3.4% had a positive urethral swab. In women in one setting in the United States, 3.7% were found to have an extragenital infection. Those under the age of 18 had the highest incidence of extragenital infection.

Guidelines

It's currently recommended that sexually active people with a vagina and uterus younger than 25 have yearly screenings for chlamydia. This can be done at the same time as the yearly Pap smear. More frequent screening may be advisable for adolescents.

For people with a vagina 25 and older, yearly screenings should be done for those at an increased risk, such as those who have a new partner, multiple partners, or are with someone who has had an STI.

Screening has been found to be very effective and to significantly lower the risk of a woman developing pelvic inflammatory disease (PID), which can lead to infertility.

MSM should be screened at least annually (both genital and rectal sites of exposure). For those with HIV (human immunodeficiency virus) or who have multiple partners, screening should be done every three to six months.

While there aren't specific recommendations for heterosexual males, screening should be strongly considered. Roughly twice as many women as men are diagnosed with chlamydia, most likely due to inadequate testing of men.

Until guidelines are set, heterosexual men who are outside of a long-term, mutually exclusive (one sexual partner) relationship should request testing, preferably on an annual basis, and more often as needed.

Requesting Testing

There are a number of reasons why healthcare providers fail to test for STIs and why you may need to initiate the discussion and request testing yourself. Even with screening guidelines in place, many cases go untested and undetected.

Make sure to request a chlamydia test, especially if one of your partners has been diagnosed with an STI, or if you are sexually active outside of a long-term mutually monogamous relationship.

Many shy away from such testing because of feelings that they will be judged for their sexual history. Know that chlamydia is extremely common and found in people from all walks of life. It only takes one sexual encounter with one person who carries the bacteria to develop the infection. 

If asking your healthcare practitioner for the test is hard for you, consider others' strategies for bringing up the subject. And if you ask and don't like the response you get, consider seeing another healthcare professional. 

Results and Follow-Ups

If you do get a positive test result, it's important to talk to any sexual partners you've had in the past two months and suggest that they see a healthcare provider for testing and treatment.

As with any form of lab tests, there is the potential for errors. Even though the sensitivity of chlamydia tests used today is good, they may still miss infections (what's known as a false-negative result). What this means is that if you have any symptoms, you should follow up with your practitioner—even if you tested negative.

There is also a small risk of false-positive results, in which a person gets a positive chlamydia test result but does not actually have the infection. This is of less concern in general, as most people tolerate the treatments for chlamydia well. Accidentally treating a few people who do not have the disease is considered better than missing those who do. 

Retesting After Treatment

Getting retested about three months after treatment for chlamydia is recommended for both men and women, even those who know their partners were also treated.

Reinfection is possible, and most cases that are found after treatment are because of this possibility, rather than the failure of the treatment itself.

Pregnant women should be retested three weeks after treatment is completed. Pregnant women at high risk should also consider getting tested again in the third trimester.

Differential Diagnosis

Vaginal discharge has many causes, ranging from bacterial vaginosis (BV) to yeast infections to chlamydia to hormonal changes. Likewise, there is a wide range of conditions that can cause pain with intercourse, bleeding between periods or during intercourse, and more.

For all people, pain and burning with urination can have many possible causes, including bladder infections and other STIs. 

So, while a healthcare professional may suspect one issue or another, if you present symptoms at all, lab tests are essential to making an accurate chlamydia diagnosis and choosing the appropriate treatment.