Test ID: GCRNA
Neisseria gonorrhoeae by Nucleic Acid Amplification (GEN-PROBE)

Diagnosing Neisseria gonorrhoeae infections

Neisseria gonorrhoeae, a gram-negative bacterium, is a common cause of sexually transmitted infection. This organism causes dysuria and urethral discharge in males with acute urethritis; complications may include pelvic inflammatory disease in women, and ascending infection resulting in gonococcal epididymitis and prostatitis in men.

Neisseria gonorrhoeae is labile and does not remain viable for sustained periods of time. Diagnosis by culture methods, rather than NAT testing, especially after extended transit times, is not recommended. Previously, culture was considered the gold standard test for diagnosis of Neisseria gonorrhoeae infections. However, the organisms are labile in vitro, and precise specimen collection, transportation, and processing conditions are required to maintain organism viability, a necessity for culturing. Nucleic acid amplification testing (NAAT), which detects DNA of the organism, does not require the organism to be alive, is much more sensitive than culture, and is now considered the preferred test for detecting Neisseria gonorrhoeae.

Improved screening rates and increased sensitivity of NAAT testing translate to increased numbers of accurately diagnosed cases. Improved detection rates resulting from both increased assay performance and patients’ easy acceptance of urine testing, combined with appropriate treatment, decrease disease burden and spread.(3-5) Early identification of infection enables sexual partners to seek testing and/or treatment as soon as possible and reduces the risk of disease spread. Prompt treatment reduces the risk of infertility in women.

Negative

A positive result indicates the presence of rRNA of Neisseria gonorrhoeae.

A negative result indicates that rRNA for Neisseria gonorrhoeae was not detected in the specimen.

The predictive value of an assay depends on the prevalence of the disease in any particular population. In settings with a high prevalence of sexually transmitted disease, positive assay results have a high likelihood of being true positives. In settings with a low prevalence of sexually transmitted disease, or in any settings in which a patient's clinical signs and symptoms or risk factors are inconsistent with gonococcal or chlamydial urogenital infection, positive results should be carefully assessed and the patient retested by other methods (eg, culture for Neisseria gonorrhoeae), if appropriate.

This report is intended for use in clinical monitoring or management of patients; it is not intended for use in medico-legal applications.

Appropriate specimen collection and handling is necessary for optimal assay performance.

Results should be interpreted in conjunction with other laboratory and clinical information.

A negative test result does not exclude the possibility of infection. Improper specimen collection, concurrent antibiotic therapy, presence of inhibitors, or low numbers of organisms in the specimen (ie, below the sensitivity of the test) may cause false-negative test results.

In low prevalence populations, positive results must be interpreted carefully as false-positive results may occur more frequently than true positive results in this setting.

This assay cannot be used to assess therapeutic success or failure, since nucleic acids from the organism may persist following antimicrobial therapy.

The presence of mucous does not interfere with this assay. However, this test requires endocervical cells, and if excess mucous is not removed prior to collection, adequate numbers of these cells may not be obtained.

No interference is expected due to:

-Blood (urine and swabs) specimens

-Lubricants and spermicides (swabs)

The effects of use of tampons, douching, specimen types other than those listed in Specimen Required, and specimen collection variables have not been determined.

Testing of urine specimens with this method is not intended to replace cervical exam and endocervical sampling for diagnosis of urogenital infection; infections may result from other causes or concurrent infections may occur.

Testing urine specimens as the sole test for identifying female patients with gonococcal infections may miss some infected individuals.

Performance estimates for urine specimens are based on evaluation of urine obtained from the first part of the urine stream; performance on midstream collections has not been determined.

1. Centers for Disease Control and Prevention. 2002. Reporting of laboratory-confirmed chlamydial infection and gonorrhea by providers affiliated with three large Managed Care Organizations–United States,1995-1999. MMWR Morb Mortal Wkly Rep 2002;51:256-259

2. Centers for Disease Control and Prevention: Screening Tests To Detect Chlamydia trachomatis and Neisseria gonorrhoeae Infections-2002. Morbidity and Mortality Weekly Report Recommendations and Reports October 18, 2002;Vol. 51;No RR-15

3. Crotchfelt KA, Pare B, Gaydos C, Quinn TC: Detection of Chlamydia trachomatis by the GEN-PROBE AMPLIFIED Chlamydia trachomatis Assay (AMP CT) in urine specimens from men and women and endocervical specimens from women. J Clin Microbiol. 1998 Feb;36(2):391-394

4. Gaydos CA, Quinn TC, Willis D, et al: Performance of the APTIMA Combo 2 assay for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in female urine and endocervical swab specimens. J Clin Microbiol. 2003 Jan;41(1):304-309

5. Chernesky MA, Jang DE: APTIMA transcription-mediated amplification assays for Chlamydia trachomatis and Neisseria gonorrhoeae. Expert Rev Mol Diagn 2006 Jul;6(4):519-525