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Lab Dept:
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Microbiology/Virology
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Test Name:
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CHLAMYDIA/GC DNA ASSAY
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General Information
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Lab Order Codes:
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CTGC
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Synonyms:
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Chlamydia trachomatis/Neisseria gonorrhoeae PCR, ProbeTec
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CPT Codes:
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87491 – Chlamydia trachomatis, amplified probe technique
87591 – Neisseria gonorrhoeae, amplified probe technique
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Test Includes:
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Strand Displacement Amplification for the direct detection of C. trachomatis and N.gonorrhoeae DNA. This test is performed on genital and urine specimens only. Refer to Chlamydia trachomatis culture and GC culture for other sources.
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Logistics
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Lab Testing Sections:
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Virology - Sendouts
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Referred to:
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Mayo Medical Laboratories (MML Test#: 84465)
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-5806
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651-220-6555
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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1 - 3 days
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Special Instructions:
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● This test is approved for endocervical swabs, male urethral swabs and male and female urine specimens only. Swabs of vaginal drainage and female urethral swabs will be rejected.
● Order Chlamydia trachomatis Culture and GC Culture for rectal, ocular and respiratory sources
● The first portion of voided urine is used because it has the highest concentration of organisms, midstream urine is unacceptable.
● Specimen site and date/time of collection are required for processing.
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Specimen
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Specimen Type:
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Endocervical swabs, male urethral swabs, or the first portion of voided urine.
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Container:
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Pink ProbeTec Culturette Direct swab for females, Blue ProbeTec Culturette Direct swab for males, sterile urine
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Volume:
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1 swab; 14-20 mL of urine
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Collection:
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Endocervical:
1. Remove the large cleaning swab from the pink Culturette Direct packaging.
2. Using the cleaning swab, remove excess mucus from the cervical os.
3. Discard the used cleaning swab.
4. Insert the foam collection swab into the cervical canal and rotate for 15-30 seconds.
5. Withdraw the swab carefully. Avoid contact with the vaginal mucosa.
6. Place swab into transport tube and cap tube.
7. Label the tube with patient information and date/time of collection.
Urethral (Males Only):
1. Remove the mini-tip swab from the blue Culturette Direct packaging.
2. Insert the swab 2-4 cm into the urethra and rotate for 3-5 seconds.
3. Withdraw the swab and place into the transport tube and cap tightly.
4. Label the tube with patient information and date/time of collection.
Urine:
1. The patient should not have urinated for at least 1 hour prior to collection.
2. Collect the first 15-20 mL of voided urine not to exceed 60 mL (the first part of the stream, not midstream). This is the portion that will contain the highest concentration of organisms. Amounts exceeding 60 mL may dilute the specimen resulting in false negative results.
3. Label with patient information and date/time of collection.
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Transport/Storage:
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Transport swabs at 2-27ºC to the Microbiology Laboratory. Once in the lab, refrigerate swab. Test within 6 days.
Transport urine at 2-8ºC to the Microbiology Laboratory. Test within 6 days.
Store urine in transport media at 2-27 ºC and test within 7 days of collection.
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Special Processing:
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None
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Sample Rejection:
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Specimen not submitted in appropriate transport container; improperly labeled specimen; midstream urine; insufficient volume; external contamination; swabs of vaginal drainage and female urethral swabs. If an unacceptable specimen is received, the physician or nursing station will be notified and another specimen requested before the specimen is discarded.
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Interpretive
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Reference Range:
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No Chlamydia trachomatis detected
No Neisseria gonorrhoeae detected
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Limitations:
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● This assay should not be used for the evaluation of suspected sexual abuse or other medico-legal situations. Additional testing is recommended in any circumstance when false positive or false negative results could lead to adverse medical, social, or psychological consequences.
● A negative test result does not exclude the possibility of infection because results are dependent on adequate specimen collection, absence of inhibitors and sufficient DNA to be detected.
● Specimens grossly contaminated with blood (>5% v/v) may inhibit amplification and produce false negative or equivocal results.
● This test cannot be used to assess therapeutic success or failure since nucleic acids from C. trachomatis and N. gonorrhoeae may persist following antimicrobial therapy.
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Methodology:
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Strand Displacement Amplification
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References:
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Cook, JH, and M Pezzlo (1992). Specimen receipt and accessioning. Section 1. Aerobic bacteriology, 1.2.1-4. In HD Isenberg (ed) Clinical Microbiology Procedures Handbook. American Society for Microbiology, Washington DC
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Miller, J Michael, and HT Holmes (1999) Specimen Collection, Transport, and Storage In PR Murray et al, (ed), Manual of Clinical Microbiology, 7th edition, American Society for Microbiology, Washington DC, pp 33-104
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Becton, Dickinson and Company Sparks MD, BD ProbeTece ET Chlamydia trachomatis and Neisseria gonorrhoeae Amplified DNA Assays package insert, L000203 10/2001
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Mayo Medical Laboratories January 2012
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Updates:
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6/14/2005: Added statement for specimen rejection of swabs of vaginal drainage and female urethral swabs.
9/27/2007: New transport media for urines and processing instructions.
1/3/2012: Testing moved from internal test to Mayo.
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