Gonorrhea testing: how is it done and how accurate is it?

Gonorrhea is a very common sexually transmitted infection (STI) that can affect the genitals, mouth, throat, eyes, and rectum. Many people who are infected with gonorrhea may never develop symptoms. However, even if a person does not have symptoms, he or she can still pass the infection on to their partner. Sexual contact of any kind can lead to this infection, particularly if you are having unprotected sex.

Screening tests are needed as most of the time, people do not have symptoms and can pass gonorrhea on to their sexual partners without either person knowing. Untreated gonorrhea can result in severe complications like pelvic inflammatory disease, ectopic pregnancy, and life-threatening disseminated gonorrheal infection.

The Centers for Disease Control and Prevention (CDC) recommend the following screening guidelines (CDC, 2015):

• Sexually active women younger than 25 years of age and older women with additional risk factors should be screened yearly

• Women who are diagnosed with gonorrhea and treated should be retested three months after treatment.

• Pregnant women should be tested at their initial visit if younger than 25 years of age; older pregnant women with additional risk factors should also be tested

• Sexually active men who have sex with men (MSM) should be tested annually at all exposure sites (urethra, rectum, pharynx)

• High-risk MSM patients should be screened every 3-6 months

• Sexually active HIV patients should be tested yearly

Anyone with symptoms of gonorrhea like penile or vaginal discharge, burning during urination, or genital sores should stop having sex and see a healthcare provider for testing and evaluation. People who have one STI are at risk of having another. Therefore, people who are diagnosed with gonorrhea should also be tested for other STIs, including chlamydia, syphilis, and HIV (CDC, 2014).

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Testing for gonorrhea looks for the presence of Neisseria gonorrhoeae (gonorrhea bacteria) in your body. Urine samples can be used to test both men and women. The most accurate way to perform the test is to collect first-catch urine. This is the initial portion of your urine stream that exits as you begin to urinate.   Sometimes, your healthcare provider will take a swab from a potentially affected area. For men, urethral swabs can be collected. For women, samples can be collected using vaginal or cervical swabs. Sample collection happens during a pelvic exam, or a woman can do it herself (self-collection). In a pelvic exam, you lie on your back on an exam table, knees bent and your feet in supports called stirrups. An instrument, called a speculum, gently opens the vagina so the cervix can be examined. Your provider will then collect a sample using a swab and send it to the laboratory for evaluation. Sometimes, cells or secretions from other areas that may be infected need to be checked, such as the rectum or throat. This can also be done using a swab or soft brush.

There are several ways to check a sample for infection. A “smear” of the sample can be placed on a microscope slide and treated with special stains (Gram stain) to see the bacteria in the specimen. Under the microscope, the bacteria look like roundish pink cells in pairs (gram-negative diplococci). Alternatively, the sample can be used to grow bacterial colonies (culture), which can then be examined. The most common technique used nowadays is called a nucleic acid amplification test (NAAT) (Morgan, 2016). This test looks for the presence of N. gonorrheae genetic material (DNA) in the sample; if it is present, then you have the infection. Before having gonorrhea testing done, you should inform your healthcare provider if you have been taking any antibiotics over the past 24 hours. Women should also let their providers know if they have been using any vaginal creams or douches, as these can affect the test results. You may be asked to wait 1-2 hours after your last urination before collecting a urine sample. Menstruation does not affect the test results. When results are reported, “negative” means no infection and “positive” means that a gonorrhea infection is present.

Traditionally, growing N. gonorrheae on plates called cultures were the gold standard for diagnosis. However, it takes time for the bacterial colonies to grow. The other methods of Gram stains and NAATs testing provide quicker results. Performing a Gram stain on a smear sample is an accurate method to diagnose gonorrhea in symptomatic men with urethral discharge. However, in people with other forms of the infection, like cervical, rectal, pharyngeal (throat), or asymptomatic gonorrhea, this method can miss infected people (Unemo, 2014). In this test, a positive result means infection, but a negative result does not exclude it. NAATs are both quick and accurate. In a NAAT, the cells are broken up, and special chemicals are used to bind to the DNA of both live and dead gonococcal cells (Unemo, 2014). NAATs are effective at detecting urogenital gonorrhea. They are somewhat less effective at detecting oropharyngeal (oral) gonorrhea, but the test is still useful; a bigger sample of cells may be needed for oropharyngeal gonorrhea (Lewis, 2015). 

Gram-stained samples take a few minutes to get results; however, these are only useful if the test comes back positive. A negative gram stain does not necessarily mean that there is no infection. It needs to be confirmed by another test, either a NAAT or culture. Cultures take three to five days for the bacterial colonies to grow. NAATs that are sent out to a laboratory typically come back with the results within one to three days. There are quicker, in-office tests that can provide results within hours. However, these are not as accurate as the NAATs sent out to a laboratory and have to be confirmed using other tests.

Many people are turning to home testing kits that allow a person to self-collect a sample and mail it to a laboratory without the intermediate step of going to a clinic. Collecting the sample at home can be less invasive since it does not involve a pelvic examination for women, as do most samples collected from a hospital setting. Men can send in a first-catch urine sample, and women can use a vaginal swab. The specimen is then sent for NAAT, and the results are as good as those from physician-collected samples (Fajardo-Bernal, 2015). Some people find this method more private and less anxiety-inducing than going to a clinic. 

However, home testing does not take the place of medical care. It is essential to follow the instructions for sample collection carefully as a good specimen is needed for accurate results. Having the test done is only the first step; you still need to see a healthcare provider and be treated for the condition. Also, you need to make your sexual partners aware of your diagnosis so that they can be tested and treated if need be.

Knowing your STI status is an effective way to make sure you stay healthy. Follow the testing guidelines and practice safe sexual habits. If you have any questions or are unsure about your need to be tested, talk with your healthcare provider. Sexual health is an integral part of your overall health and should be maintained.

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Current version

August 28, 2019

Written by

Chimene Richa, MD

Fact checked by

Tzvi Doron, DO

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About the medical reviewer

Tzvi Doron, DO

Dr. Tzvi Doron is Board Certified in Family Medicine by the American Board of Family Medicine.