How Chlamydia Is Diagnosed

Chlamydia is a sexually transmitted infection 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

We mention self-checks only to emphasize that chlamydia can only be properly diagnosed in the clinic with 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, keep in mind that the majority of people do not have symptoms with a chlamydia infection. Only 5 percent to 30 percent of women and 10 percent of men will have symptoms with their infection.

Labs and Tests

There are a few different tests that may be done to look for the presence of chlamydia. These can be performed if you have symptoms or as a routine screening if you are sexually active.

Common Tests

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

  • Urine specimen
  • Urethral swab (men)
  • Endocervical swab (women)
  • Vaginal swab (women)

Physicians and clinics differ in which tests they prefer.

It is possible to test for chlamydia on a urine sample. However, not all doctors 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 the above list of tests doesn't include a Pap smear. If you've had a recent gynecological exam, which should have involved that test as a matter of standard, don't assume that you've been tested for chlamydia; a Pap cannot detect the associated bacteria. 

Likewise, if you've been tested for another sexually transmitted infection/disease, don't assume that you've been tested for chlamydia. Not only does chlamydia require its own test, but the treatments for some of the other STIs/STDs are ineffective against chlamydia.

What to Expect

The way that doctors test for chlamydia is somewhat different for women and men. This is due to the locations that chlamydia infects in each sex.

  • Women: Your gynecologist will most likely use a speculum to view your cervix. She will retrieve a sample from your cervix using a small swab, which will get sent to a lab. 

    Less commonly, a vaginal swab may be done. Recent studies suggest that vaginal swabs that women do themselves are just as accurate (if not more) than those done by healthcare professionals. That said, in most circumstances, a physician will recommend that she do the swab, whether endocervical or vaginal.

    If you are opting for a urine test, be sure to come to your healthcare professional's office with a full bladder. 
  • Men: Your doctor 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 doctors perform urine tests for chlamydia. However, you should feel comfortable asking whether or not getting a urine test for chlamydia is an option. You can also call your doctor in advance to see if urine testing is available.

Chlamydia testing is improving, and tests often come back within just a few hours, allowing rapid treatment of infections. 

Rectal and Oral Swaps

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

Your healthcare professional may still end up opting to give you a different test, but it's good for her to know about this history regardless.

Neither the rectal nor oral swab are currently approved for testing, but research suggests that doing these extragenital tests is important. For example, a 2017 study found that among men who have sex with men (MSM), 13 percent had a rectal chlamydia infection but only 3.4 percent had a positive urethral swab. In women (in an urban setting in the United States), 3.7 percent were found to have an extragenital infection. Those under the age of 18 had the highest incidence of extragenital infection.

Screening Guidelines

It's currently recommended that sexually active women age 25 and under have yearly screening for chlamydia. This can be done at the same time as the yearly Pap smear. More frequent screening may be advisable for adolescents.

For women older than 25, yearly screening should be done for those at an increased risk, such as those who have a new partner, multiple partners, or especially, if they are with someone who has had an STD.

Screening has been found to be very effective and to significantly lower the risk of a woman developing pelvic inflammatory disease (PID). Since PID can lead to infertility, among other problems, this is extremely noteworthy.

Men who have sex with men (MSM) should be screened at least annually (both genital and rectal sites of exposure). For those with HIV or multiple partners, screening should be done every three to six months. A 2013 study found that regular screening of MSM could reduce the risk of chlamydia and HIV by 15 percent and 4 percent, respectively. (Chlamydia increases the risk of becoming infected with HIV.)

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, men who are outside of a long-term monogamous relationship should request testing, preferably on an annual basis, and more often as needed.

Requesting Testing

There are a number of reasons why doctors fail to test for STDs—and why you may need to initiate the discussion and request the test 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/STD, 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 broaching the subject. And if you ask and don't like the response you get, consider finding a new healthcare professional. 

Test Results and Follow-Ups

If you do have a positive test, it's important to talk to any sexual partners you've had in the past two months and suggest that they see a doctor 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 (result in false-negatives). What this means is that if you have any symptoms, you should follow up with your doctor—even if you had a negative result.

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

Re-Testing After Treatment

Guidelines for re-testing after treatment don't exist, except in pregnant women; they should be retested three weeks after treatment is completed. Pregnant women at high risk should also consider getting tested again in the third trimester. Certainly, anyone who has persistent symptoms should undergo re-testing.

Differential Diagnoses

Vaginal discharge in women has many causes, ranging from bacterial vaginosis 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 with intercourse, and more.

For both men and women, pain and burning with urination can have many possible causes, including bladder infections and other STDs. 

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. In addition, it's possible for someone to have chlamydia and another infection at the same time, and testing can help sort of if that's the case.

We have good tests to find chlamydia, and when positive, good treatments to cure the infection. But without a diagnosis, treatment doesn't happen, and without treatment, complications such as infertility may occur.

Sources:

Centers for Disease Control and Prevention. Chlamydia—CDC Fact Sheet (Detailed). Updated 10/04/17. https://www.cdc.gov/std/chlamydia/stdfact-chlamydia-detailed.htm

Frati, E., Fasoli, E., Martinelli, M. et al. Sexually Transmitted Infections: A Novel Screening Strategy for Improving Women's Health in Vulnerable Populations. International Journal of Molecular Sciences. 2017 Jun 20;18(6). pii: E1311.

Kiridou, M., Vriend, H., Lugner, A. et al. Modelling the Impact of Chlamydia Screening on the Transmission of HIV Among Men Who Have Sex with Men. BMC Infectious Diseases. 2013. 13(1L:436.

Lunny, C., Taylor, D., Hoang, L. et al. Self-Collected Versus Clinician-Collected Sampling for Chlamydia and Gonorrhea Screening: A Systematic Review and Meta-Analysis. PLoS One. 2015. 10(7):e0132776.

Mustanski, B., Feinstein, B., Madkins, K., Sullivan, P., and G. Swann. Prevalence and Risk Factors for Rectal and Urethral Sexually Transmitted Infections From Self-Collected Samples Among Young Men Who Have Sex With Men Participating in the Keep It Up! 2.0 Randomized Controlled Trial. Sexually Transmitted Diseases. 2017. 44(8):483-488.

Van Der Pol, B., Williams, J., Fuller, D., Taylor, S., and E.Hook. Combined Testing for Chlamydia, Gonorrhea, and Trichomonas by Use of the BD Max CT/GC/TV Assay with Genitourinary Specimen Types. Journal of Clinical Microbiology. 2016. 55(1):155-164.