Test Id : MCTGC

This test is used for specimens that are not FDA approved for this assay. Acceptable non-FDA-approved specimen types are ocular swabs, and peritoneal fluid. For FDA-approved specimen types, order CGRNA / Chlamydia trachomatis and Neisseria gonorrhoeae, Nucleic Acid Amplification, Varies.

Specimen source is required.

Swab specimens must be collected using an Aptima Collection Unisex Swab (T583), or Aptima Collection Multitest Swab (T584). These swabs are contained in the Aptima Collection Kit.

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

See Specimen Required

Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in non-FDA-approved specimen types

This test is not intended for use in medico-legal applications.

This test is not useful for the detection of Chlamydia pneumoniae.

Chlamydia is caused by the obligate intracellular bacterium Chlamydia trachomatis and is the most prevalent sexually transmitted bacterial infection in the United States.(1,2) In 2010, 1.3 million documented cases were reported to the CDC.(2) Given that 3 out of 4 infected women and 1 out of 2 infected men will be asymptomatic initially, the actual prevalence of disease is thought to be much greater than reported. The organism causes genitourinary infections in women and men and may be associated with dysuria as well as vaginal, urethral, or rectal discharge. In women, complications include pelvic inflammatory disease, salpingitis, and infertility. Approximately 25% to 30% of women who develop acute salpingitis become infertile.(2) Complications among men are rare but include epididymitis and sterility. Rarely, genital chlamydial infection can cause arthritis with associated skin lesions and ocular inflammation (Reiter syndrome). C trachomatis can be transmitted from the mother during delivery and is associated with conjunctivitis and pneumonia. Finally, C trachomatis may cause hepatitis and pharyngitis in adults.

Once detected, the infection is easily treated by a short course of antibiotic therapy. Annual chlamydia screening is now recommended for all sexually active women age 25 years and younger and for older women with risk factors for infection, such as a new sex partner or multiple sex partners. The CDC also recommends that all pregnant women be given a screening test for Chlamydia infection.(2) Repeat testing for test-of-cure is not recommended after treatment with a standard treatment regimen unless patient compliance is in question, reinfection is suspected, or the patient's symptoms persist. Repeat testing of pregnant women, 3 weeks after completion of therapy, is also recommended to ensure therapeutic cure.(2)

Gonorrhea is caused by the bacterium Neisseria gonorrhoeae. It is also a very common sexually transmitted infection (STI), with 301,174 cases of gonorrhea reported to CDC in 2009.(2,3) Many infections in women are asymptomatic and the true prevalence of gonorrhea is likely much higher than reported. The organism causes genitourinary infections in women and men and may be associated with dysuria as well as vaginal, urethral, or rectal discharge. Complications include pelvic inflammatory disease in women and gonococcal epididymitis and prostatitis in men. Gonococcal bacteremia, pharyngitis, and arthritis may also occur. Infection in men is typically associated with symptoms that would prompt clinical evaluation. Given the risk for asymptomatic infection in women, screening is recommended for women at increased risk of infection (eg, women with previous gonorrhea or other STI, inconsistent condom use, new or multiple sex partners, and women in certain demographic groups such as those in communities with high STI prevalence).(2,3) The CDC currently recommends dual antibiotic treatment due to emerging antimicrobial resistance.(2)

Culture was previously considered to be the gold standard test for diagnosis of C trachomatis and N gonorrhoeae infections.(2) However, organisms are labile in vitro, therefore, precise specimen collection, transportation, and processing conditions are required to maintain organism viability, which is necessary for successful culturing. In comparison, nucleic acid amplification testing (NAAT) provides superior sensitivity and specificity and is now the recommended method for diagnosis in most cases.(4-6) Immunoassays and non-amplification DNA tests are also available for C trachomatis and N gonorrhoeae detection, but these methods are significantly less sensitive and less specific than NAAT.(2)

Improved screening rates and increased sensitivity of NAAT testing have resulted in an increased number of accurately diagnosed cases of both chlamydia and gonorrhea.(2-6) Improved detection rates result from both the increased performance of the assay and the patients' easy acceptance of urine testing. Early identification of infection enables sexual partners to seek testing and/or treatment as soon as possible and reduces the risk of disease spread. Prompt treatment reduces the risk of infertility in women.

Negative

A positive result indicates that rRNA of Chlamydia trachomatis and/or Neisseria gonorrhoeae is present in the specimen tested and strongly supports a diagnosis of chlamydial/gonorrheal infection.

A negative result indicates that rRNA for C trachomatis and/or N gonorrhoeae was not detected in the specimen.

The predictive value of an assay depends on the prevalence of the disease in any particular population. In settings with a high prevalence of sexually transmitted disease, positive assay results have a high likelihood of being true positives. In settings with a low prevalence of sexually transmitted disease, or in any setting in which a patient's clinical signs and symptoms or risk factors are inconsistent with gonococcal or chlamydial urogenital infection, positive results should be carefully assessed and the patient retested by other methods (eg, culture for N gonorrhoeae), if appropriate.

A negative result does not exclude the possibility of infection. If clinical indications strongly suggest gonococcal or chlamydial infection, additional specimens should be collected for testing. A result of indeterminate indicates that a new specimen should be collected.

This test has not been shown to cross react with commensal (nonpathogenic) Neisseria species present in the oropharynx.

This report is intended for use in clinical monitoring or management of patients; it is not intended for use in medico-legal applications.

Appropriate specimen collection and handling is necessary for optimal assay performance.

Results should be interpreted in conjunction with other laboratory and clinical information.

A negative test result does not exclude the possibility of infection. Improper specimen collection, concurrent antibiotic therapy, presence of inhibitors, or low numbers of organisms in the specimen (ie, below the sensitivity of the test) may cause false-negative test results.

In low-prevalence populations, positive results must be interpreted carefully as false-positive results may occur more frequently than true-positive results in this setting.

In general, this assay should not be used to assess therapeutic success or failure, since nucleic acids from these organisms may persist for 3 weeks or more following antimicrobial therapy.

No interference is expected with swab specimens due to:

-Blood

-Lubricants and spermicides

Chlamydia trachomatis

Accuracy:

1. Clinical Specimens

Non-FDA approved specimen types were collected in Hologic (GEN-PROBE) APTIMA collection devices according to the manufacturer's instructions and tested using the APTIMA Combo 2 assay on the Tigris DTS System. Results were compared to those obtained by other CLIA-certified laboratories using the Tigris system. All specimens were within product insert stability requirements at the time of testing on the Tigris system. Clinical specimens were stored frozen until the time of testing.

Non-FDA Approved Sources for detection of C trachomatis (see additional spiking data below):

*Additional studies using raw peritoneal fluid in lieu of swab collection were performed for a more concise specimen collection and enhanced recovery. One mL of peritoneal fluid was added to a Hologic APTIMA specimen transfer kit then spiked with C trachomatis and Neisseria gonorrhoeae at the limit of detection.

IFU-inclusion forming units

2. Spiked Specimens:

Analyte-negative ocular (n=32)and peritoneal fluid (n=30) specimens were spiked at the approximate limit of detection (LOD) and tested to supplement clinical specimen validation data (see analytical sensitivity validation data below).

Percent concordance by specimen type:

3. Total Accuracy (Clinical and spiked specimens combined):

*All collection devices are manufactured by Hologic (GEN-PROBE) for use with the Aptima assay.

**Positive and negative status are based on the result by the comparator method (clinical specimens) or expected result (spiked specimens).

Analytical Sensitivity/LOD:

The LOD of this assay was established at 3 IFU (inclusion forming units) using a quantified whole organism control from Zeptometrix. The LOD was confirmed in all non-FDA approved specimens that will be accepted for testing with this assay (, ocular specimens). At least 30 clinical specimens of each source grouping were spiked with C trachomatis at 3 IFU/assay. Results are as follows:

According to the package insert, the LOD for detection of C trachomatis using FDA approved specimens and collection devices is 1 IFU per assay, with a range of 3 to 0.1 IFU per assay. Therefore, the LOD for non-FDA approved specimens falls within this range and is considered acceptable.

Analytical Specificity:

To augment the specificity panel performed by Hologic (GEN-PROBE) as outlined in the APTIMA product insert, an additional panel was tested by the Tigris DTS System using the APTIMA COMBO 2 Assay. Negative patient matrix specimens collected in Hologic collection devices were spiked with specificity panel organisms and tested. Organisms were chosen based on their ability to cause disease similar to C trachomatis, or be normal flora in non-FDA approved specimen sources. The assay did not cross-react with any members of the specificity panel.

N gonorrhoeae

Accuracy:

1. Clinical Specimens:

Non-FDA approved specimen types were collected in Hologic (GEN-PROBE) APTIMA collection devices according to the manufacturer's instructions and tested using the APTIMA Combo 2 assay on the Tigris DTS System. Results were compared to those obtained by other CLIA-certified laboratories using the Tigris system. All specimens were within product insert stability requirements at the time of testing on the Tigris system. Clinical specimens were stored frozen until the time of testing.

Non-FDA Approved Sources for detection of N gonorrhoeae (see additional spiking studies below):

*Additional studies using raw peritoneal fluid in lieu of swab collection were performed for a more concise specimen collection and enhanced recovery. One mL of peritoneal fluid was added to a APTIMA specimen transfer kit then spiked with C trachomatis and N gonorrhoeae at the limit of detection.

2. Spiked Specimens:

Negative specimens were spiked at the approximate limit of detection (LoD) and tested to supplement clinical specimen validation data (see analytical sensitivity validation data below).

3. Total Accuracy (Clinical and spiked specimens combined):

*All collection devices are manufactured by Hologic for use with the Aptima assay

**Positive and negative status are based on the result by the comparator method (clinical specimens) or expected result (spiked specimens)

Analytical Sensitivity (LOD)

The LOD was established by preparing dilutions of N gonorrhoeae (ATCC strain 43069). The LOD was determined to be 12.5 CFU (colony forming units)/assay. Although specimens diluted to a final concentration of 12.5 CFU/assay gave 100% positive results, we chose only to test the analytical sensitivity claim in the product insert, which is 50 CFU/assay. The LOD was confirmed in all non-FDA approved specimens that will be accepted for testing with this assay (ocular specimens). Clinical specimens of each source/grouping were spiked with N gonorrhoeae at 50 CFU/assay and tested with positive and negative controls as per standard protocol.

Summary of Results:

Analytical Specificity:

To augment the specificity panel performed by Hologic as outlined in the APTIMA product insert, an additional panel was tested by the Tigris DTS System using the APTIMA COMBO 2 Assay. Analyte-negative patient specimens collected in Hologic collection devices were spiked with specificity panel organisms and tested. Organisms were chosen based on their ability to cause disease similar to N gonorrhoeae or be normal flora in non-FDA approved specimen sources. The assay did not cross-react with any members of the specificity panel.

1. Centers for Disease Control and Prevention. 2014. Recommendations for the laboratory-based detection of Chlamydia trachomatis and Neisseria gonorrhoeae, 2014. MMWR Morb Mortal Wkly Rep. 2014;63:1-18

2. Centers for Disease Control and Prevention: Sexually Transmitted Diseases Treatment Guidelines, 2015. MMWR Morb Mortal Wkly Rep. 2015 Jun 5;64(RR-03):1-137.

3. Centers for Disease Control and Prevention. 2002. Reporting of laboratory-confirmed chlamydial infection and gonorrhea by providers affiliated with three large Managed Care Organizations-United States, 1995-1999. MMWR Morb Mortal Wkly Rep. 2002;51:256-259

4. Crotchfelt KA, Pare B, Gaydos C, Quinn TC: Detection of Chlamydia trachomatis by the GEN-PROBE AMPLIFIED Chlamydia trachomatis Assay (AMP CT) in urine specimens from men and women and endocervical specimens from women. J Clin Microbiol. 1998 Feb;36(2):391-394

5. Gaydos CA, Quinn TC, Willis D, et al: Performance of the APTIMA Combo 2 assay for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in female urine and endocervical swab specimens. J Clin Microbiol. 2003 Jan;41(1):304-309

6. Chernesky MA, Jang DE: APTIMA transcription-mediated amplification assays for Chlamydia trachomatis and Neisseria gonorrhoeae. Expert Rev Mol Diagn. 2006 Jul;6(4):519-525

The Hologic Aptima Combo 2 Assay combines the technologies of target capture, transcription-mediated amplification, and dual kinetic assay. The detection of the rRNA amplification product sequences (amplicon) is achieved using nucleic acid hybridization. Single-stranded chemiluminescent DNA probes are labeled and combine with amplicon to form stable RNA:DNA hybrids. Light emitted from the labeled RNA:DNA hybrids is measured as photon signals in a luminometer.(Package insert: Hologic APTIMA Combo 2 Assay. 502446 Hologic, Inc; Rev. 005 06/2018)

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This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

MCRNA-87491

MGRNA-87591

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