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Test Code CT/NG PCR Chlamydia trachomatis and Neisseria gonorrhoeae PCR

Important Note

Additional Codes

Cerner

NextGen

Chlam/GC PCR

Chlamydia/ Gonorrhoeae PCR

CT/GC PCR

 

Useful For/ Methodology

The Xpert® CT/NG Assay, performed on the GeneXpert® Instrument Systems, is a qualitative in vitro real-time PCR test for the automated detection and differentiation of genomic DNA from Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (NG) to aid in the diagnosis of chlamydial and gonorrheal urogenital disease. It is a moderate complexity, closed cartridge system.

The assay may be used to test the following specimens from asymptomatic and symptomatic individuals: female and male urine, vaginal, endocervical swab, and patient-collected vaginal swab (collected in a clinical setting).

Patient Preparation

None

Collection Instructions

  • Urine (males and females)
    • Patient should not have urinated for at least 1 hour prior to specimen collection.
    • Female patient should not cleanse the labial area prior to collecting specimen.
    • Male patient should NOT cleanse the tip of the penis.
    • Collect about 20-50 ml of first-catch urine into a urine cup without preservatives.

 or  or 

  • If specimen volume is less than 7 mL then Chlamydia trachomatis and Neisseria gonorrhoeae, Nucleic Acid Amplification, Varies (CGRNA) needs to be ordered and processed.
    • Label the specimen with patient name, second identifier, source, and date/time of collection.
    • Vaginal/Endocervical Specimen​​​​
      • Remove excess mucus from the cervical os using the large individually wrapped cleaning swab provide with the kit.
      • Discard the cleaning swab.
      • Use the provided collection swab to collect the sample. Gently rotate the swab clockwise for 10 to 30 seconds in the endocervical canal to insure adequate sampling.
      • Insert the swab in to the Xpert Transport Reagent tube.
      • Recap and invert or gently shake the tube 3-4 times
      • Label the specimen with patient name, second identifier, source, and date/time of collection.

Specimen Processing

  • Unpreserved urine specimens
    • Stability

Specimen

Transport and

Storage

Temperature (°C)

Storage

Time

Female Urine

4° C

 

 

15-30° C

8 days

 

24 hours

Male Urine

4° C

 

 

15-30° C

8 days

 

3 days

 

    • To preserve urine
      • Mix specimen in primary container well
      • Insert the provided disposable transfer pipette into the urine cup so that the tip is near the bottom if the cup. Transfer approximately 7 ml of urine into the Xpert Urine Transport Reagent tube. The correct volume of urine has been added when the level reaches the black dashed line on the label of the Xpert CT/NG urine transport tube.
      • Replace the cap.
      • Mix by inverting the reagent tube 3-4 times.
      • Label the secondary container per laboratory procedures.
  • Preserved urine stability

Specimen

Xpert

Assay

Transport and

Storage

Temperature (°C)

Storage

Time

Female Urine in

Transport Reagent

CT/NG

Assay

2-15° C

 

 

2-30° C

45 days

 

3 days

Male Urine in

Transport Reagent

CT/NG

Assay

 

2-30° C

 

 

45 days

 

  • Swab specimen stability

Specimen

Xpert

Assay

Transport and

Storage

Temperature (°C)

Storage

Time

Endocervical  or

Vaginal swab in Xpert Swab

Transport Reagent

 

 

CT/NG

Assay

 

2-30° C

 

 

60 days

Result Reporting and Reference Values

Reference Range
  • C. trachomatis PCR: Not Detected
  • N. gonorrhoeae PCR: Not Detected

Critical Ranges

N/A

Reflex Testing

None

Limitations

  • The Xpert CT/NG Assay has not been evaluated with patients who are currently being treated with antimicrobial agents active against CT or NG.
  • Because the detection of CT and NG is dependent on the DNA present in the sample, reliable results are dependent on proper sample collection, handling and storage.
  • With endocervical and patient-collected vaginal specimens, assay interference may be observed in the presence of: blood (>1% v/v) or mucin (>0.8% w/v).
  • With urine specimens, assay interference may be observed in the presence of: blood (>0.3% v/v), mucin (>0.2% w/v), bilirubin (>0.2 mg/mL), or Vagisil feminine powder (>0.2% w/v).
  • Collection and testing of urine specimens with the Xpert CT/NG Assay is not intended to replace cervical exams and endocervical sampling for diagnosis of urogenital infection. Other genitourinary tract infections can be caused by other infectious agents.
  • The effects of other potential variables such as vaginal discharge, use of tampons, douching, and specimen collection variables have not been determined.
  • A negative test result does not exclude the possibility of infection because test results may be affected by improper specimen collection, technical error, specimen mix-up, concurrent antibiotic therapy, or the number of organisms in the specimen which may be below the sensitivity of the test.
  • Additional testing is recommended in any circumstance when false positive or false negative results could lead to adverse medical, social, or psychological consequences.
  • The predictive value of an assay depends on the prevalence of the disease in any particular population.
  • Positive results may be observed after successful antibiotic treatment due to target nucleic acids from residual non-viable chlamydia.
  • The Xpert CT/NG Assay has not been evaluated with patients who are currently being treated with antimicrobial agents active against CT or NG.
  • As with many diagnostic tests, results from the Xpert CT/NG Assay should be interpreted in conjunction with other laboratory and clinical data available to the physician.
  • Interfering Substances
    • With vaginal/endocervical specimens, assay interference may be observed in the presence of:
      • Blood at a concentration greater than 1% v/v;
      • Mucin at a concentration greater than 0.8% w/v.
    • With urine specimens, assay interference may be observed in the presence of:
      • Blood at a concentration greater than 0.3% v/v;
      • Mucin at a concentration greater than 0.2% w/v;
      • Bilirubin at a concentration greater than 0.2 mg/mL (20 mg/dL);
      • Vagisil feminine powder at a concentration greater than 0.2%