Test Id : MGRNA

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 GCRNA / 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 Neisseria gonorrhoeae for non-FDA approved specimen types

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

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.(1,2) 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 and 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).(1,2) 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 N gonorrhoeae infection. 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.(2-5) Immunoassays and non-amplification DNA tests are also available for N gonorrhoeae detection, but these methods are significantly less sensitive and less specific than NAAT.(2-5)

Improved screening rates and increased sensitivity of NAAT testing have resulted in an increased number of accurately diagnosed cases.(2-5) 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 the presence of rRNA of Neisseria gonorrhoeae.

A negative result indicates that rRNA for 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 settings in which a patient's clinical signs and symptoms or risk factors are inconsistent with gonococcal urogenital infection, positive results should be carefully assessed and the patient retested by other methods (eg, culture for N gonorrhoeae), if appropriate.

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.

No interference is expected with swab specimens due to:

-Blood

-Lubricants and spermicides

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 Neisseria 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 GenProbe APTIMA specimen transfer kit then spiked with Chlamydia trachomatis and N gonorrhoeae at the limit of detection.

IFU - inclusion forming units

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 (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 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 (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. 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. 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

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. 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

4. 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

5. 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.

87591

Sample Reports

Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports

International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports