Chlamydia trachomatis & Neisseria gonorrhoeae (CT/NG) DNA

Useful For

Detection of Chlamydia trachomatis and/or Neisseria gonorrhoeae DNA from genital specimens.

 

Test Components

Reporting Name Available separately Always performed
C. trachomatis DNA NO YES
N. gonorrhoeae DNA NO YES

 

Testing Algorithm

C. trachomatis + N. gonorrhoeae multiplex PCR.

N. gonorrhoeae-positive specimens are subjected to re-extraction and repeat testing as confirmation.

 

Indications for Testing

Cervicitis, urethritis, pelvic inflammatory disease (PID)

 

Method Name

Real-time Polymerase Chain Reaction (PCR)

 

Reporting Name

C. trachomatis DNA

N. gonorrhoeae DNA

 

Aliases

C. trachomatis

CT

Chlamydia

LGV

Lymphogranuloma venereum

N. gonorrhoeae

NG

STI

Sexually transmitted infection

STD

Sexually transmitted disease

Pharyngitis

Conjunctivitis

Endocervical swab and vaginal swab (Female)

 

Container/Tube: Cobas® PCR Female Swab Collection Kit

Collection Instructions:

  1. Remove excess mucus from exocervix with medium cleaning swab provided in Cobas PCR collection kit and discard. This step is important in removing mucus which may prohibit nucleic acid extraction.
  2. Insert second medium swab into endocervix, rotate swab for 15 to 30 seconds to ensure adequate sampling.
  3. Withdraw swab.
  4. Holding tube upright, verify that all Cobas PCR collection medium is at bottom of transport tube. Unscrew cap of transport tube, fully insert swab into tube, and break swab at score line. Screw cap on securely.

 

Note:   1. Specimen source is required.

2. Spermicidal agents and feminine powder sprays interfere with the assay and should not be used prior to collection.

 

 

First Void Urine (Male and Female)

 

Container/Tube: Cobas® PCR Urine Sample Kit

Specimen Volume: 10 mL urine

Collection Instructions:

  1. Patient should not have urinated for at least 1 hour prior to specimen collection.
  2. Patient/ health care provider should collect first portion of a voided urine (first part of stream) into a sterile, plastic, preservative-free specimen collection container.

Note: Specimen source is required.

 

OTHER SPECIMEN SOURCES*

Nasopharyngeal, rectal and conjunctival specimens collected in Cobas® PCR Female Swab Collection Kit have not been validated at the Newfoundland & Labrador Public Health Laboratory.

 

Transport Temperature

Specimen Room temperature Refrigerated Frozen
Cobas Swab YES YES NO*/**
Cobas Urine YES YES NO*

*Endocervical swab specimens collected with the cobas® PCR Female Swab Sample Kit and male and female urine collected with the cobas® PCR Urine Sample Kit may be stored at 2-30°C for up to 12 months once the specimens have been stabilized in cobas® PCR Media.

**Vaginal swab specimens collected with the cobas® PCR Female Swab Sample Kit may be stored at 2-30°C for 90 days once the specimens have been stabilized in cobas® PCR Media.

 

Reject Due To

Specimens other than Cobas collection device

 

Useful For

The C. trachomatis & N. gonorrhoeae multiplex PCR assay detects CT and NG infections from endocervical swab or first void urine specimens from symptomatic or asymptomatic individuals.

 

Clinical Information

Chlamydia trachomatis (CT) is the causative infectious agent for a variety of diseases in men: urethritis, proctitis, conjunctivitis, epididymitis, and Reiter’s Syndrome. Among woman, the consequences of chlamydial infections are severe if left untreated; CT infection can cause urethritis, cervicitis, conjunctivitis, endometritis, salpingitis (with subsequent infertility or ectopic pregnancy) and perihepatitis. Infants from infected mothers can develop conjunctivitis, pharyngitis, and pneumonia.

 

Chlamydia trachomatis (CT) is the most commonly diagnosed and reported sexually transmitted bacterial infection in Canada. The number of reported cases in Canada in 2006 was > 65,000 (202 per 100,000) and has been increasing annually. This, however, is an underestimate as the disease is often asymptomatic and therefore undiagnosed. CT infections are more common among females between the ages of 15-24 and young men aged 20-29.

 

Genital infections caused by Chlamydia trachomatis often go unrecognized as the majority of infected persons are asymptomatic. An estimated 3 out of 4 infected women and 1 out of 2 infected men will be asymptomatic initially.

 

Previously, culture was considered the gold standard test for diagnosis of Chlamydia trachomatis infections. However, organisms are labile in vitro and stringent specimen collection, transportation, and processing conditions are required to maintain organism viability, a necessity for culturing. Immunoassay tests are significantly less sensitive and specific than nucleic acid amplification testing (NAAT). NAAT is much more sensitive than culture, and is now considered the preferred test for detecting Chlamydia trachomatis.

 

Clinical manifestations of Neisseria gonorrhoeae (NG) infections are numerous. In men, acute urethritis presents itself after 1 – 10 day incubation period with urethral discharge and dysuria. The majority of NG infections are symptomatic. Acute epididymitis is the most common complication, especially in young men. In woman, the primary site of infection is the endocervix. There is a high prevalence of co-infections with CT, Trichomonas vaginalis and bacterial vaginosis; many women remain asymptomatic and therefore remain undiagnosed. Predominant symptoms are increased discharge, dysuria, and intermenstrual bleeding. Pelvic inflammatory disease can occur in 10 – 20% of woman, combined with endometritis, salpingitis, tubo-ovarian abscess, pelvic peritonitis, and perihepatitis. Other gonococcal infected sites are the rectum, pharynx, conjunctiva, and to a lesser degree the disease presents as disseminated gonococcal infection. Infants from infected mothers can develop conjunctivitis.

 

Epidemiology in Newfoundland and Labrador can be found in the Communicable Disease Report:

Gonococcal: – http://www.health.gov.nl.ca/health/publichealth/cdc/mdr/Gonorrhoea_v28n1_June_2011.pdf

Chlamydia: http://www.health.gov.nl.ca/health/publichealth/cdc/mdr/Chlamydia_June_2011.pdf

 

Reference Values

NOT DETECTED

 

Interpretation

CT

DETECTED: indicates the presence of Chlamydia trachomatis DNA. This assay is not intended as a test of cure as non-viable CT may be detected when performed < 3 weeks after completion of therapy. In cases of treatment failure isolation/culture should be attempted.

 

NOT DETECTED: absence of Chlamydia trachomatis DNA.

 

INDETERMINATE: the specimen submitted contained substances inhibitory to the assay. Please recollect a specimen to complete follow up.

 

NG

DETECTED: indicates the presence of N. gonorrhoeae DNA. This assay is not intended as a test of cure as non-viable CT may be detected when performed < 3 weeks after completion of therapy. In cases of treatment failure isolation/culture should be attempted.

 

NOT DETECTED: absence of N. gonorrhoeae DNA.

 

INDETERMINATE: the specimen submitted contained substances inhibitory to the assay. Please recollect a specimen to complete follow up.

 

Clinical Reference

Essig, A. 2007. Chlamydia and Chlamydophilia, p. 1021-1035. In Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., and Pfaller, M. A. Manual of Clinical Microbiology, 9th ed., vol. 2. ASM Press, American Society for Microbiology, Washington, DC.

 

Stamm, W. E., and Batteiger, B. E. 2010. Chlamydia trachomatis (Trachoma, Perinatal Infections, Lymphogranuloma Venereum, and Other Genital Infections, p. 2443-2461. In Mandell, D., Bennett, J. E., and Dolin, R. 2010. Principles and practice of infectious diseases, 7th ed., vol. 2. Churchill Livingstone, Elsevier, Philadelphia, PA.

 

Roche Molecular Systems Inc. Cobas® 4800 CT/NG Test: Package insert. Roche Diagnostics GmbH, Mannheim.

 

Rockett, R., Goire, N., Limnios, A., Turra, M., Higgens, G., Lambert, S.B., Bletchly, C., Nissen, M.D., Sloots, T.P., and Whiley, D.M. 2010. evaluation of the cobas 4800 CT/NG test for detecting Chlamydia trachomatis and Neisseria gonorrhoeae. Sex Transm Infect. 86:470-3.

 

Janda, WM., and Gaydos, C. 2007. Neisseria, p601 – 620. In Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., and Pfaller, M. A. Manual of Clinical Microbiology, 9th ed., vol. 2. ASM Press, American Society for Microbiology, Washington, DC.

Real-time PCR amplification

 

Status Days Analytic Time Maximum Laboratory Time Specimen Retention
Routine Monday – Friday 7h 48h 1 week

 

Method Description

The Cobas® 4800 CT/NG Test for Chlamydia trachomatis and Neisseria gonorrhoeae is based on nucleic acid extraction and simultaneous PCR amplification and target DNA sequences using both CT and NG specific complementary primer pairs and real-time detection of cleaved fluorescent-labelled CT and NG specific oligonucleotide detection probes. The amplification targets for CT are the cryptic plasmid and genomic ompA gene; for NG are within the DR-9 region.

 

When CT DNA is detected (both cryptic plasmid and ompA) in submitted specimen the result is reported. However, if NG is detected in a specimen the specimen is re-extracted and testing repeated to as confirmation.

 

Due to the need to monitor emergence of drug resistant NG the PHL is requesting that a concurrent specimen is submitted for culture isolation to allow antimicrobial susceptibility testing. See Neisseria gonorrhoeae culture or contact your Regional microbiology laboratory to arrange isolation.

 

Performance Characteristics

CT detection includes trachoma serotypes (A – C), genital infection serotypes (E – K), and lymphogranuloma venereum (LGV) serotypes (LV 1 – 3) as well as the Swedish Strain (nvCT).
CTNG Performance

 

 

Performance characteristics of the cobas 4800 CT/NG test for urine and swab specimens

 

Reference results: cobas 4800 performance: Additional cobas 4800 results:
Pos (n) Neg (n) Sens (%) Spec (%) NPV (%) PPV (%) Failed , n (%) Invalid, n (%)
C. trachomatis
cobas 4800 Urine (n=496) Pos 86 2 94.5 99.5 98.8 97.7 6 (1.0) 3 (0.6)
Neg 5 395
Swab (n=404) Pos 23 0 92.0 100 99.5 100 0 (0.0) 1 (0.2)
Neg 2 378
N. gonorrhoeae
cobas 4800 Urine (n=318) Pos 13 0 92.9 100 99.7 100 4 (1.3) 2 (0.6)
Neg 1 298
Swab (n=180) Pos 9 1 100 99.4 100 90.0 0 (0.0) 0 (0.0)
Neg 0 170

 

Rockett et al. 2010.

 

Performing Laboratory Location

Newfoundland & Labrador Public Health Laboratory

St. John’s

 

 
 

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