Can this test be used if the patient has no symptoms?

Yes. Most chlamydia and many gonorrhoea infections are asymptomatic, particularly in women, so screening sexually active individuals at risk is a core public-health strategy to prevent complications such as pelvic inflammatory disease and infertility.

Why is first-void urine recommended?

The first portion of the urinary stream washes organisms from the urethra, maximising detection sensitivity. Mid-stream or dilute urine lowers yield, so patients should not have urinated for at least one hour before collection.

How soon after exposure can infection be detected?

Nucleic-acid amplification becomes positive within days of infection, but testing within the first two weeks of exposure may miss very early infection. Guidelines recommend testing at least 2 weeks post-exposure, or earlier if symptoms develop.

Is a test-of-cure needed after treatment?

Routine test-of-cure is not recommended for most patients because nucleic-acid tests can remain positive for several weeks due to non-viable RNA. It is indicated in pregnant women, when adherence is uncertain, or if symptoms persist. Delay testing at least 3 weeks after completing therapy.

Does a negative urogenital test exclude infection at other sites?

Yes. This test detects only urogenital infection; pharyngeal and rectal chlamydia and gonorrhoea require separate specimen collection and are clinically important in men who have sex with men and individuals with relevant exposure.

Can menstruation affect the result?

Blood can inhibit nucleic-acid amplification and cause invalid results, though modern assays are more robust. Some laboratories recommend deferring collection until menstruation ends, but practitioners should follow the performing laboratory's guidance.

What if the patient has already started antibiotics?

Recent antimicrobial therapy reduces bacterial RNA and can produce false-negative results. Ideally collect the specimen before starting treatment; if already treated, note this on the requisition and interpret a negative result cautiously, considering repeat testing or presumptive treatment of partners.

BML-INF-085infectious diseaseUSA

Chlamydia/Neisseria gonorrhoeae RNA, TMA, Urogenital

The CT/NG RNA TMA test detects Chlamydia trachomatis and Neisseria gonorrhoeae ribosomal RNA in urogenital specimens using transcription-mediated amplification. It is the first-line diagnostic for the two most common bacterial STIs, offering high sensitivity from first-void urine and enabling opportunistic screening, partner notification, and public-health control of infections that frequently…

Biomarkers

Urine (random)

Sample

2–3 business days

Turnaround

Fasting

What is the CT/NG RNA TMA test?

The Chlamydia/Neisseria gonorrhoeae RNA transcription-mediated amplification test detects the ribosomal RNA of the two most common bacterial causes of sexually transmitted urogenital infection. Both organisms frequently produce asymptomatic infection, particularly in women, yet carry substantial morbidity — untreated chlamydia is the leading preventable cause of tubal infertility, and gonorrhoea causes pelvic inflammatory disease and, increasingly, infections resistant to first-line therapy. Practitioners order this dual nucleic-acid amplification test as the first-line diagnostic for suspected urogenital infection and as a screening tool in sexually active populations at elevated risk. TMA offers higher sensitivity than culture or antigen methods and permits testing of first-void urine, which has transformed access to screening by removing the need for invasive sampling in many clinical scenarios. The test is central to public-health control of chlamydia and gonorrhoea through case detection, treatment, and partner notification.

What does the CT/NG RNA TMA test measure?

CT rRNA(Chlamydia trachomatis ribosomal RNA)

Range: Not detectedOptimal: Not detectedDetected / Not detected

Chlamydia trachomatis is an obligate intracellular bacterium infecting columnar epithelial cells of the urogenital tract, rectum, pharynx, and conjunctiva. Most urogenital infections in women are asymptomatic but untreated infection ascends to cause pelvic inflammatory disease, tubal factor infertility, and chronic pelvic pain. In men urethritis is more frequently symptomatic though a substantial minority remain asymptomatic. Transcription-mediated amplification (TMA) targets bacterial ribosomal RNA, present in many copies per organism, offering very high analytical sensitivity.

Detection of C. trachomatis RNA confirms active infection requiring antimicrobial treatment and partner notification. Untreated chlamydia is the leading preventable cause of tubal infertility and ectopic pregnancy; timely detection through screening of sexually active young adults and those with new or multiple partners is a core public-health intervention. A positive result mandates treatment and concurrent testing for other sexually transmitted infections.

NG rRNA(Neisseria gonorrhoeae ribosomal RNA)

Range: Not detectedOptimal: Not detectedDetected / Not detected

Neisseria gonorrhoeae is a Gram-negative diplococcus that infects mucosal epithelium of the urethra, endocervix, rectum, pharynx, and conjunctiva. Ascending infection in women causes pelvic inflammatory disease; disseminated gonococcal infection, though uncommon, manifests as arthritis-dermatitis syndrome or, rarely, endocarditis or meningitis. Transcription-mediated amplification detects gonococcal ribosomal RNA with high sensitivity, exceeding that of culture while preserving specificity.

Detection of N. gonorrhoeae RNA confirms gonococcal infection requiring prompt antimicrobial therapy, currently dual therapy with ceftriaxone and azithromycin in most jurisdictions to address rising resistance. Co-infection with chlamydia is common, so dual testing is standard. Gonorrhoea is a notifiable infection and expedited partner therapy is recommended where legally permitted.

Why is the CT/NG RNA TMA test ordered?

Screening of sexually active women aged under 25 years and sexually active men who have sex with men, in line with national guidelines
Investigation of urethritis, cervicitis, mucopurulent discharge, dysuria, or pelvic pain suggestive of pelvic inflammatory disease
Evaluation of patients with a new sexual partner, multiple partners, or a partner known to have a sexually transmitted infection
Opportunistic screening in sexual health, contraception, abortion-care, and antenatal services
Post-exposure assessment after sexual assault or unprotected intercourse with a partner of unknown infection status
Test-of-cure three weeks after treatment in pregnant women, or where adherence or re-exposure is uncertain
Investigation of neonatal conjunctivitis or pneumonitis when maternal infection is suspected
Contact tracing and partner notification following a newly diagnosed index case

Sample collection and turnaround

Sample type

Urine (random)

Fasting required

Collection method

At-home collection kit

Turnaround

2–3 business days

Collection notes

First-void urine (the first 20–30 mL of the urinary stream) collected at home using the kit provided. Patients should not have urinated for at least one hour before collection. The specimen is stabilised in a transport tube and returned by prepaid courier. Avoid collection during or immediately after antimicrobial therapy.

Specimen requirements

First 20–30 mL of the urinary stream in the preservative tube supplied. Do not overfill. Return within 24 hours at ambient temperature; the preservative stabilises nucleic acids for several days. Note any recent antibiotic use on the requisition.

What can affect CT/NG RNA TMA results?

reducesRecent antimicrobial therapy

Antibiotics with activity against chlamydia or gonorrhoea reduce bacterial load and RNA copy number, potentially yielding false-negative results if the test is performed during or immediately after therapy; delay testing or interpret cautiously.

variableSpecimen contamination or inhibitors

Urine specimens containing blood, mucus, or chemical inhibitors can interfere with nucleic-acid amplification; laboratories typically report such specimens as invalid and request a repeat collection.

reducesCollection timing after exposure

Nucleic-acid tests become positive shortly after infection, but specimens collected within the first few days of exposure may miss very early infection; clinical guidelines recommend testing 2 weeks post-exposure.

reducesNon-first-void urine

TMA sensitivity is optimised using the first 20–30 mL of the urinary stream, which washes organisms from the urethra; mid-stream or dilute specimens lower yield.

variableMenstruation or vaginal bleeding

Blood can inhibit amplification and cause invalid results; some laboratories recommend deferring collection until menstruation has ended, though modern assays are less affected.

elevatesCross-reactivity with commensal Neisseria

Early-generation gonorrhoea assays showed cross-reaction with non-pathogenic Neisseria; contemporary TMA assays targeting 16S rRNA have high specificity, but pharyngeal specimens remain a concern and may require culture confirmation.

What do CT/NG RNA TMA results mean?

Elevated

A 'detected' result for either organism confirms active infection and mandates antimicrobial treatment according to national guidelines, partner notification, and testing for co-infection with the other pathogen and additional sexually transmitted infections including HIV and syphilis. For gonorrhoea, ensure that local or national antimicrobial-resistance surveillance informs therapy. Pregnant women with chlamydia require a test-of-cure.

Normal

'Not detected' for both organisms indicates no evidence of chlamydia or gonorrhoea at the time of sampling. This does not exclude infection at other anatomical sites (pharynx, rectum) if only urogenital specimens were tested, nor does it exclude other causes of urogenital symptoms. Re-screening intervals depend on risk: annual screening is recommended for sexually active young women and more frequent screening for men who have sex with men.

Reduced

Not applicable — the test is qualitative (detected vs not detected).

Note: A negative test during the window period (within 2 weeks of exposure) may not exclude early infection; repeat testing if clinical suspicion is high. Persistent symptoms after a negative test warrant investigation for other pathogens and non-infectious causes. Test-of-cure is not routinely recommended except in pregnancy or when treatment adherence is uncertain, as nucleic-acid tests can remain positive for several weeks post-treatment due to non-viable RNA. Pharyngeal and rectal infections require separate specimen collection and are not detected by urogenital testing.

Frequently asked questions

A detected result for either chlamydia or gonorrhoea confirms active infection requiring antimicrobial treatment, partner notification, and screening for other sexually transmitted infections. Both are curable with appropriate antibiotics.

How to access the CT/NG RNA TMA test

The CT/NG RNA TMA reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.

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About this page

Published: October 7, 2026

Last reviewed: October 7, 2026

References:

Workowski KA, et al. Sexually transmitted infections treatment guidelines, 2021. MMWR Recomm Rep (CDC). (2021)
UK National Guideline for the Management of Infection with Chlamydia trachomatis (BASHH). (2018)
Canadian guidelines on sexually transmitted infections — Chlamydia and gonorrhoea (Public Health Agency of Canada). (2020)
ACOG Committee Opinion No. 645: Screening for gonorrhoea and chlamydia — a renewed call to action. Obstet Gynecol. (2015)
European guideline on the management of Chlamydia trachomatis infections (IUSTI). (2020)

This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.