What tests confirm gonorrhea?

Gonorrhea is a sexually transmitted infection (STI) caused by the bacterium Neisseria gonorrhoeae. It can infect the genitals, rectum, and throat. Some key points about gonorrhea testing:

Table of Contents

Summary

Nucleic acid amplification tests (NAATs) are the preferred method of testing for gonorrhea. They are highly accurate and can be performed on urine samples or swabs.

Culture testing can also confirm gonorrhea but is less commonly used now.
A positive gonorrhea test should always be followed up with a test for other STIs like chlamydia.
Retesting several weeks after treatment is important to confirm the infection has been cured.

Nucleic Acid Amplification Tests (NAATs)

Nucleic acid amplification tests (NAATs) are the most widely used and accurate tests to diagnose gonorrhea. They amplify the genetic material of the bacteria to detect its presence. NAATs can be performed on urine samples or on swabs taken from the infected site such as the urethra, cervix, rectum, or throat.

Some advantages of NAATs:

Very high sensitivity and specificity – over 95%. This means false positives and false negatives are rare.

Results available rapidly, usually within 1-2 days.
Non-invasive testing possible through urine samples.
Can simultaneously test for other STIs like chlamydia.

Because of these benefits, the CDC recommends NAATs as the first choice for gonorrhea testing in symptomatic individuals. They are also recommended for screening high-risk individuals like sexually active women under 25 years old.

Types of NAATs

There are various NAAT methods that can detect N. gonorrhoeae:

Polymerase chain reaction (PCR) – This amplifies Neisseria DNA to detect it. PCR for gonorrhea can be performed on urine, genital, rectal, or pharyngeal samples.

Strand displacement amplification (SDA) – SDA uses enzymes to amplify DNA and RNA of the bacteria.
Transcription-mediated amplification (TMA) – TMA amplifies RNA sequences of N. gonorrhoeae.
DNA hybridization tests – These use synthetic DNA probes that bind to complementary Neisseria sequences.

While the technology differs between the tests, they are all NAATs that deliver highly accurate results.

Gonorrhea Culture

Gonorrhea can also be diagnosed by culturing the bacteria from a swab sample. A sterile swab is used to collect a sample from the infected site like the cervix or urethra. This swab is inoculated onto a culture medium under laboratory conditions ideal for bacterial growth.

Key aspects of gonorrhea culturing:

If N. gonorrhoeae grows on the culture medium, it confirms gonorrhea.
Culturing can also determine antibiotic susceptibility of the bacteria – useful to guide treatment.
Samples for culture need to be quickly transported to the laboratory under appropriate conditions.

Disadvantages compared to NAATs include longer time to get results (2-3 days) and lower sensitivity.

Due to disadvantages of culture testing, NAATs are now preferred over growing cultures. But culturing still has a role when a person has persistent gonorrhea symptoms despite a negative NAAT result. It can also be done after treatment to ensure the gonorrhea has been cured.

Supplementary Tests

Alongside the main diagnostic test, supplementary tests give useful additional information when investigating suspected gonorrhea:

Microscopic examination

A Gram stain of the sample may show Gram-negative diplococci bacteria under the microscope. This provides preliminary visual evidence of gonorrhea infection. However, microscopy alone cannot definitively diagnose or rule out gonorrhea.

Testing for coinfections

Someone diagnosed with gonorrhea should also be tested for other STIs like chlamydia, syphilis, and HIV. Coinfections are common because the risk factors are similar. NAATs that simultaneously test for several infections can be useful.

Antibiotic susceptibility

If a gonorrhea culture is done, antibiotic susceptibility of the bacteria should be tested. This guides the choice of antibiotic for treatment. Resistance rates to certain antibiotics are increasing so up-to-date local susceptibility patterns should inform treatment.

Who should be tested for gonorrhea?

Gonorrhea testing is recommended for:

Anyone with signs/symptoms of infection – discharge, burning urination, abdominal pain, etc.
Sexual contacts of people diagnosed with gonorrhea in the prior 60 days.

Pregnant women – gonorrhea can cause serious health problems in newborns.
Men who have sex with men and people with HIV – should have regular screening.
Sexually active women under 25 years old – should be screened annually.

In most cases, a NAAT on a urine sample or genital swab is performed for screening. However, rectal and pharyngeal swabs may also be needed to test for gonorrhea infections at those sites.

When to test

Symptomatic individuals – Testing should be done immediately if gonorrhea symptoms are present.
After potential exposure – If someone has had unprotected sex with a partner subsequently diagnosed with gonorrhea, they should get tested within 1-2 weeks of exposure (the incubation period).

Screening for at-risk groups – Guidelines recommend annual gonorrhea screening for sexually active women under 25 years old and men who have sex with men.
During pregnancy – Pregnant women should be tested within the first trimester. Retesting may be warranted in the third trimester if at ongoing risk.
Before IUD insertion – Women should be screened for gonorrhea before getting an intrauterine device inserted.

Test of cure – Retest 3-4 weeks after completing treatment for gonorrhea to confirm the infection has resolved.

Interpreting Test Results

Interpreting gonorrhea test results:

A positive NAAT or culture result confirms gonorrhea infection.

Negative tests do not completely rule out gonorrhea. Testing should be repeated if symptoms persist.
Individuals treated for gonorrhea should have a test of cure, even if asymptomatic.
False positive NAAT results are unusual but can occur.

Indeterminate or equivocal results warrant a repeat test, ideally using a different NAAT method.

A confirmed gonorrhea diagnosis requires prompt treatment and contact tracing. Sexual partners should be notified, tested, and treated.

Limitations of Gonorrhea Testing

While current gonorrhea tests are highly accurate, some limitations to be aware of:

NAATs only detect nucleic acid of N. gonorrhoeae. They cannot inform antibiotic susceptibility.
Culturing gonorrhea gives useful information on antibiotic resistance but has lower sensitivity than NAATs.
No available test can detect all gonorrhea infections. The bacteria may not be present at the site sampled for testing.

Asymptomatic screening may miss cases. Most guidelines focus on testing symptomatic individuals.
Following up positive tests and verifying treatment success remains challenging.

Ongoing research aims to improve gonorrhea diagnostics. Ideal tests would be low-cost, non-invasive, highly sensitive at all infection sites, and able to assess antibiotic resistance.

Takeaway Messages

NAATs on urine or swab samples are the preferred method to diagnose gonorrhea, with over 95% accuracy.
Culture testing also confirms infection but is less commonly performed now.
Individuals at risk due to symptoms or sexual exposure should get tested promptly.

Retest after treatment to confirm the infection has resolved.
Improvements in diagnostic technology could enhance gonorrhea screening and control.

Conclusion

Gonorrhea is a prominent sexually transmitted disease that can have serious reproductive health consequences if left untreated. Effective diagnosis through NAATs, culture, or ideally both is crucial in managing gonorrhea. Individuals at risk should have access to timely, affordable testing. Continued innovation to improve gonorrhea diagnostics will support public health efforts to reduce the burden of this infection.