Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in Urine, Endocervical, Vaginal, and Urethral Specimens
Target amplification nucleic acid probe, qualitative
1 – 4 days
ThinPrep® Solution in Aptima® Transport Media
ThinPrep® Solution, unprocessed
Sexually transmitted diseases (STDs) continue to be a major cause of deteriorating reproductive health throughout the world. Chlamydia trachomatis and Neisseria gonorrhoeae remain as two of the most common causes of STDs in the United States.1 C. trachomatis infections have comprised the largest proportion of all STDs reported to the CDC since 1994, with a reported 1,244,180 cases in 2009 for a rate of 409.2/100,000 population. This was a 2.8% increase in rate from that reported in 2008.1,2 The increase in reported chlamydial infections during the last 20 years reflects the expansion of chlamydia screening activities and the use of increasingly sensitive assays for the detection of C. trachomatis. The CDC recommends annual chlamydia screening of all sexually active women younger than 25 years of age.3
In 2009, there were 301,174 cases of N. gonorrhoeae infections reported for a rate of 99.1/100,000 population. This rate was a 10.5% decrease since 2008. The national gonorrhea rate declined by 74% between 1975 and 1997 following the implementation of a national gonorrhea control program in the mid-1970s. However, since 1997, these rates have reached a plateau and are not continuing to decline.1,2 Infections due to both C. trachomatis and N. gonorrhoeae are a major cause of pelvic inflammatory disease (PID) in the U.S. and both have been shown to facilitate the transmission of HIV as well.
Rapid and sensitive methods for the laboratory diagnosis of these two agents have been developed, making it reasonable to test for both simultaneously when the diagnosis of an STD is being considered.2 The estimate of mixed infections with both agents can be as high as 40%, making it important to consider ordering both agents when sending material off to the laboratory for testing. Nucleic acid amplification tests (NAAT) are recommended for detection of reproductive tract infections caused by C. trachomatis and N. gonorrhoeae infections in men and women with and without symptoms. NAAT should be used for diagnosing both C. trachomatis and N. gonorrhoeae in women with cervicitis; testing can be performed on vaginal, cervical, or urine samples. In men with urethritis, NAAT testing of urine or urethral swabs is recommended.3
Both C. trachomatis and N. gonorrhoeae cause urethritis in the male and cervicitis in the female. A significant number of cases, however, remain asymptomatic in both males and females. In addition, both can cause epididymitis and rectal infections in the male, and PID in the female.
Neonates, who contract chlamydial infection during birth, can develop inclusion conjunctivitis and/or pneumoniae; pregnant women can infect their newborns, causing ophthalmia neonatorum; gonorrheal infections can produce joint infections, pharyngitis, and disseminated disease.
Cleveland Clinic Laboratories offers a target amplification nucleic acid probe (APTIMA, Gen-Probe, Inc, San Diego, CA) for the laboratory diagnosis of C. trachomatis and N. gonorrhoeae from urethral and urine specimens from males suspected of these infections, and from cervical, vaginal, and urine samples from females. Numerous articles have been published demonstrating the excellent performance of NAAT testing for the diagnosis of both of these STD agents.4-8
The laboratory diagnosis of Neisseria gonorrhoeae can include culture of urethral or cervical specimens, gram stain of the urethral secretions in symptomatic males, detection by specific nucleic acid gene probes, and amplification of N. gonorrhoeae nucleic acids. Amplification of N. gonorrhoeae nucleic acids has been shown to be a very sensitive and specific method of detection.4,5 The sensitivity is equivalent to culture, but it is not fraught by the problem of organism fragility that can easily occur with delays in specimen transport.
Although culture or the use of a nucleic acids probe can be employed for the detection of C. trachomatis, nucleic acid amplification is the most sensitive method, with studies indicating that it may be up to 40% more sensitive than culture. The same assay that detects Chlamydia trachomatis nucleic acids is also used by Cleveland Clinic Laboratories to detect Neisseria gonorrhoeae nucleic acids, thus providing a convenient approach to dual detection.
Specimen Collection & Transport
Acceptable specimens include urethral, endocervical, and vaginal swabs, as well as urine. A vaginal swab is optimal for screening asymptomatic females, while a first-catch urine is optimal for screening asymptomatic men.
The Aptima® Unisex Swab Specimen Collection Kit for urethral or endocervical specimens contains a white cleaning swab to be used for removing excess mucus. The blue swab must be used for collection of specimens that are submitted for testing.
- For urethral specimens:
- Patients should not urinate within 1 hour prior to specimen collection.
- Insert the blue shaft swab 2 to 4 cm into the urethra.
- Gently rotate swab clockwise for 2 to 3 seconds and withdraw carefully.
- For endocervical specimens:
- Remove excess mucus using cleaning swab and then insert blue shaft swab into the endocervical canal.
- Rotate swab for 10-30 seconds in the endocervical canal to ensure adequate sampling and withdraw carefully (avoid contact with vaginal mucosa).
Place swab into the transport tube and carefully break at the scoreline. Use care to avoid splashing contents. Discard top portion of swab shaft and recap transport tube tightly.
Maintain the specimen at 2ºC to 30ºC.
The Aptima® Multitest Swab Transport Media Kit is optimal for testing asymptomatic women.
- For vaginal specimens:
- Hold the swab with forefinger and thumb covering the scoreline (do not hold the shaft below the scoreline).
- Carefully insert the swab about 2 inches into the vagina and gently rotate the swab for 10-30 seconds.
- Make sure the swab touches the walls of the vagina so that moisture is absorbed by the swab, then withdraw the swab without touching the skin.
- While holding the swab in the same hand, unscrew the cap from the tube, being careful not to spill contents of the tube.
Immediately place the swab in the transport tube and carefully break swab shaft at score line against side of the tube. Use care to avoid splashing contents. Discard top portion of swab shaft and recap transport tube tightly.
Maintain the specimen at 2ºC to 30ºC.
The Aptima® Urine Specimen Collection Kit is used for the collection and transport of male or female urine specimens for chlamydia and/or gonorrhea testing.
- For urine specimens:
- Patients should not urinate within one hour of collection.
- Collect the first catch urine (approximately 20-30 ml of initial urine stream; collecting larger volumes of urine will reduce test sensitivity).
- Within 24 hours of collection, transfer 2 mL of urine into the Aptima® urine transport tube using the disposable pipette provided in the collection kit. The correct volume of urine has been added when the fluid level is between the black lines on the transport tube label.
Maintain the specimen at 2ºC to 30ºC.
Alternatively, if a ThinPrep® vial is being used for a Liquid Cytology PAP Test, the same sample can be submitted for detection of C. trachomatis and N. gonorrhoeae as well.9
The assay can only be performed on ThinPrep® vials if 1 mL of Cytyc PreservCyt Solution is transferred to an Aptima® Specimen Transfer Tube before the specimen is processed in Cytology for a PAP test.
Maintain the specimen at 2ºC to 30ºC.
Amplification is performed Monday through Friday. Internal controls are run with each specimen in order to detect any inhibitors in the sample.
Results will be reported as “positive for C. trachomatis and/or N. gonorrhoeae by amplification” when the relative light unit (RLU) result is above our positive cut-off value.
Within a narrow range of RLU results, as determined by the assay manufacturer, an “equivocal result” will be reported with a request that a repeat specimen be submitted.
If the internal control indicates inhibition, and the result is negative for C. trachomatis and/or N. gonorrhoeae, the report will be: “Inhibition detected; N. gonorrhoeae, and/or C. trachomatis, if present, would not be detectable. Please send an additional specimen.”
All results for N. gonorrhoeae and/or C. trachomatis that are lower than the laboratory’s derived positive cut-off, but within the instrument derived positive results, will be confirmed with a repeat amplification assay before reports are released. This is done to avoid any problems with false-positive results that might occur with low positive results.10
There is currently no FDA clearance for use of amplification assays on specimens outside of the genitourinary tract. Culture is recommended for testing specimens from the throat, eye, or rectal area. However, a laboratory can validate the use of NAAT for rectal and pharyngeal specimens. In addition, for specimens obtained from infants and children, or if the information from the laboratory is to be used for legal purposes, culture is the preferred method.7
Since NAAT is more sensitive, it may be run in conjunction with culture for purposes of treatment decision-making. Although “test-of-cure” samples are not recommended from patients in whom the diagnosis has previously been made within the last 4-6 weeks, if required, a culture is the preferred request.
If a culture is needed for any of these purposes, the collection swab for Neisseria gonorrhoeae needs to be placed into a culturette and NOT the Aptima® transport tube, and a specific request for culture should be made.
1. Centers for Disease Control and Prevention. Sexually Transmitted Disease Surveillance, 2009. Atlanta, GA: U.S. Department of Health and Human Services; November 2010. Printed copies and the on-line version of this report can be obtained at the following website: http://www.cdc.gov/std/pubs.
3. Centers for Disease Control and Prevention. Sexually transmitted Diseases treatment Guidelines. MMWR. 2010;59(RR#2):1-110.
4. Chernesky M, Martin DH, Hook EW et al. Ability of Aptima CT and Aptima GC assays to detect Chlamydia trachomatis and Neisseria gonorrhoeae in male urine and urethral swabs. J Clin Microbiol. 2005;43:127-31.
5. Gaydos CA, Quinn TC, Willis D, Weissfeld A, Hook EW, Martin DH, Ferrero DV, Schachter J. Performance of the APTIMA Combo 2 assay for the multiplex detection of Chlamydia trachomatis and Neisseria gonorrhoeae in female urine and endocervical swab specimens. J Clin Microbiol. 2003;41:304-309.
6. Fang J, Husman C, Dasilva L et al. Evaluation of self collected vaginal swab, first void urine, and endocervical swabs for the detection of C. trachomatis and N. gonorrhoeae in adolescent females. J Pediatr Adolesc Gynecol. 2008;21:355-60.
7. Blake DR, Maldeis N, Barnes MR et al. Cost-effectiveness of screening strategies for C. trachomatis using cervical swabs, urine, and self-obtained vaginal swabs in a sexually transmitted disease clinic setting. Sex Transm Dis. 2008;35:649-55.
8. Schachter J, Chernesky MA, Willis DE, et al. Vaginal swabs are the specimens of choice when screening for C. trachomatis and N. gonorrhoeae: results from a multicenter evaluation of the Aptima assays for both infections. Sex Transm Dis. 2005;32:725-8.
9. Chernesky M, Jang D, Smieja M et al. Validation of the Aptima Combo 2 assay for detection of C. trachomatis and N. gonorrhoeae in Sure-Path liquid-based pap test samples taken with different collection devices. Sex Transm Dis. 2009;36:581-2.
10. Farrell, DJ. Evaluation of AMPLICOR Neisseria gonorrhoeae PCR using cppB nested PCR and 16S rRNA PCR. J Clin Microbiology. 1999;37:386-90.