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Epic Test Code LAB1376 Chlamydia and Gonorrhoeae Screen by Nucleic Acid Amplified Probe


Genprobe for Chlamydia and GC (N. gonorrhoeae); CT and GC screen

Specimen Type

Acceptable Sources: Vaginal, Cervical, Endocervical, and Urethral 

SWAB: BLUE Swab submitted in Genprobe Aptima Unisex Swab, Specimen Collection Kit for Endocervical and Male Urethral Swab Specimens.

Swab: Aptima Unisex Swab Collection Kit


Acceptable sources: Urine

URINE: Urine submitted in Aptima Urine Specimen Collection Kit.

Urine: Aptima Urine Specimen Collection Kit


Storage Requirements

SWAB: After collection, transport and store swab specimen at transport and store at 2  to 30° Celsius. Specimen must be tested within 60 days of collection


URINE: After collection, transfer into Urine Specimen Transport Tube within 24hrs, transport and store at 2 to 30° Celsius. Specimen must be tested within 30 days of collection.

Causes for Rejection

For both specimen types:

Mislabeled or unlabeled specimen will be rejected

Sources other than Vaginal, Cervical, Endocervical, Urine, or Urethral



Specimen swab or specimen tube other than provided by Genprobe

White cleaning swab submitted instead of blue collection swab

No liquid in vial submitted

            White cleaning and blue swab submitted together              

            No swab submitted in Aptima 2 vial


Urine samples must be transfered into the APTIMA urine specimen tube within 24 hours of collection. If > 24 hours sample will be rejected.

After urine has been added, the liquid level in the urine transport tube must fall between the two black indicator lines on the tube label. Otherwise, the specimen will be rejected.

Days of Analysis

M, W, F

Additional Information

Patient Preparation:

Patient should not have urinated for at least one hour prior to sampling.


Additional Information:

  1. NAAT testing for GC/Chlamydia has not been FDA approved for rectal or oral sources. Therefore, we cannot perform these tests on these sources. Suggest ordering GC and Chlamydia cultures, particularly in cases that may have legal implications.
  2. Culture isolation is acceptable for detecting C. trachomatis in rectal or pharyngeal swab specimens.
  3. Culture isolation is well established for detecting N. gonorrhoeae in rectal or pharyngeal swab specimens.
  4. To request a culture for Neisseria gonorrhoeae, see entry for GC Culture: Any Source (GC)
  5. N. gonorrhoeae and Chlamydia trachomatis infections are NYSDOH reportable communicable diseases. The NYSDOH will be notified of all positive results
  6. For off campus positive results, the ordering provider is required to report these to NYSDOG using form DOH389

Available STAT



The Gen-Probe APTIMA Combo 2 Assay is a second generation NAAT that utilizes target capture, Transcription-Mediated Amplification (TMA), and Dual Kinetic Assay (DKA) technologies to streamline processing, amplify target rRNA, and detect amplification, respectively

Reference Values

Reference Range: Chlamydia DNA Probe
Population Units Reference Range
All Populations none Negative


Reference Range: GC DNA Probe
Population Units Reference Range
All Populations none Negative


CPT Code

87491, 87591

Last Updated



  1. To ensure collection of cells infected with Chlamydia, columnar epithelial cells lining the endocervix should be sampled. If excess mucus is not removed, sampling of these cells is not ensured.
  2. Reliable results are dependent on adequate specimen collection. Because the transport system used for this assay does not permit microscopic assessment of specimen adequacy, training of clinicians in proper specimen collection techniques is necessary. Refer to the package insert of the appropriate GEN-PROBE specimen collection kit.
  3. Therapeutic failure or success cannot be determined with the APTIMA Combo 2 Assay since nucleic acid may persist following appropriate antimicrobial therapy
  4. Results from the APTIMA Combo 2 Assay should be interpreted in conjunction with other laboratory and clinical data available to the clinician.
  5. A negative result does not preclude a possible infection because results are dependent on adequate specimen collection. Test results may be affected by improper specimen collection, technical error, specimen mix-up, or target levels below the assay limit of detection.
  6. For the endocervical swab, male urethral swab and urine specimen clinical studies, performance characteristics for detecting CT and GC are derived from high prevalence populations. Positive results in low prevalence populations should be interpreted carefully with the understanding that the likelihood of a false positive may be higher than a true positive.
  7. The APTIMA Combo 2 Assay is not intended for the evaluation of suspected sexual abuse or for other medico-legal indications. For those patients for whom a false positive result may have adverse psycho-social impact, the CDC recommends retesting.