Chlamydia/Gonococcus - Client-provided Aliquot

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Turnaround Time: 2 - 3 days
CPT Code:

87491, 87591

Test Type: 1 mL PreservCyt® fluid
Reference Range:

Negative; no Chlamydia trachomatis or Neisseria gonorrhoeae detected.


Detect Chlamydia trachomatis and/or Neisseria gonorrhoeae.


“Because cytology/HPV testing and STD testing address different clinical questions, aliquot removal may not be suitable for all clinical situations. Physicians and other persons responsible for ordering clinical tests should be familiar with the following.

• There is no evidence of degradation of cytology results by aliquot removal, however, this cannot be ruled out for all specimens. As with any subsampling step in anatomic pathology, chance misallocation of diagnostic cells may occur if they are very rare. If negative results from the specimen do not fit with the clinical impression, a new specimen may be necessary.

• Aliquot removal from low-cellularity may leave insufficient material in the PreservCyt® sample vial for preparation of a satisfactory ThinPrep® Pap Test™ slide.

• Aliquot removal may leave insufficient material in the PreservCyt® sample vial for performance of ancillary testing (ie, reflexive HPV testing) using the residual specimen following preparation of a ThinPrep® Pap Test™.

• Cocollection of separate samples for the ThinPrep® Pap Test™ and STD testing may be considered in lieu of aliquot removal.

• When opting for concurrent cytologic and STD testing, providers should consider risk and clinical history (eg, disease prevalence, patient age, sexual history, or pregnancy) as well as specimen suitability (ie, exudates of bleeding) that can impact diagnostic reliability.1,2

1. ThinPrep 2000® System Operator's Manual Addendum, 70983-001-B001 Rev A.

2. ThinPrep 3000® System Operator's Manual Addendum, 70557-001-B001 Rev A.

Collection Details:

Collection Instructions:

Specimens submitted for this test must be handled using precautions necessary to prevent cross-contamination. This training should be provided by Hologic.

Gen-Probe® Aptima® swab transport or Gen-Probe® Aptima® specimen transfer kit with 1 mL of PreservCyt® fluid (do not use swabs provided with Aptima® kit).

ThinPrep® preservative vial processing: ThinPrep® instructions for removal of material are specifically listed in the ThinPrep® 2000 and ThinPrep® 3000 System Operator's manual Addenda. These instructions include the following statement. “Good laboratory practices should be followed to avoid introducing contaminants into either the PreservCyt® sample vial (ThinPrep® vial) or the aliquot. It is recommended to use powder-free gloves and an individually wrapped, disposable pipetting device with an aerosol barrier tip that is sized appropriately for the volume being withdrawn and dispensed. You should not use serological pipettes. In order to minimize the potential for cross contamination, aliquot removal should be performed in an appropriate location outside an area where amplification is performed.”

LabCorp uses the following procedure and believes it is consistent with the previous instructions as well as with the amplified assay that will be performed on the specimen to be sent. Note: For testing, aliquots must be transferred to Aptima® specimen transport tubes or Aptima® Unisex specimen transport tubes (both referred to as “Aptima® tube” in the following procedure) from ThinPrep® vials within seven days of specimen collection when ThinPrep® vials are stored at 15°C to 30°C.

Aliquot Removal Procedure

1. Put on clean gloves.

2. Wipe down work surfaces and pipettors with 1:1 bleach:water solution.

3. Allow bleach to contact work surfaces and pipettors for at least one minute and then follow with a water rinse.

4. Cover the bench with clean, plastic-backed absorbent laboratory bench covers.

5. Retrieve ThinPrep® vials that are to have aliquots removed.

6. In the specimen transfer area, place a test tube rack containing a sufficient number of Aptima® tubes to the number of ThinPrep® Pap specimens being tested for Ct/Ng.

7. Label each Aptima® tube with the appropriate specimen label.

8. Put on clean gloves before proceeding to specimen transfer.

9. Loosen the cap on the Aptima® tube. Be sure not to touch the pierceable foil cap of the Aptima® tube.

10. Vortex the ThinPrep® vial for 8 to 12 seconds at high speed. Caution: The desired aliquot must be removed immediately after vortexing the vial to ensure homogeneity of the sample.

11. Uncap the vial and place it on the work surface with the threads facing up.

12. Using a pipetting device with an aerosol barrier tip, immediately withdraw a 1 mL aliquot from the ThinPrep® vial.

13. Uncap the Aptima® tube and retain the cap in your hand.

14. Carefully dispense the aliquot into the appropriately labeled Aptima® tube.

15. Recap the Aptima® tube tightly. Gently invert the tube two to three times to ensure complete mixing of the specimen.

16. Dispose of the pipette tip into a biohazard bag containing absorbent material soaked with bleach.

17. Recap the ThinPrep® Liquid Pap specimen for Pap smear processing.

18. Store the aliquot in Aptima® tube at 15°C to 30°C for transport to LabCorp.

19. Put on clean gloves and repeat steps 8 to 18 with subsequent specimens. To reduce the chance of contaminating other specimens, work with one ThinPrep® Liquid Pap specimen at a time.

20. Remember that prior to processing for Pap smear in the ThinPrep® instrumentation, a volume of PreservCyt® equal to that removed for testing must be added back to the vial.

Maintain specimen at room temperature or refrigerate (2°C to 30°C). Aliquots must be transferred to the Aptima® tube within seven days of collection.